Ga2O3 Schottky Barrier Diodes Research Articles

A 1.6 kV Ga2O3 Schottky Barrier Diode with a Low Reverse Current of 1.2 × 10-5 A/cm2 Enabled by Field Plates and N Ion-Implantation Edge Termination.

In this work, by employing field plate (FP) and N ion-implantation edge termination (NIET) structure, the electrical performance of the β-Ga2O3 Schottky barrier diode (SBD) was greatly improved. Ten samples of vertical SBDs were fabricated to investigate the influence of the relative positions of field plates (FPs) and ion implantation on the device performance. The device with the FP of 15 μm and the ion implantation at the edge of the Schottky electrode exhibited a breakdown voltage (Vbr) of 1616 V, a specific on-resistance (Ron,sp) of 5.11 mΩ·cm2, a power figure of merit (PFOM) of 0.511 GW/cm2, and a reverse current density of 1.2 × 10-5 A/cm2 @ -1000 V. Compared to the control device, although the Ron,sp increased by 1 mΩ·cm2, the Vbr of the device increased by 183% and the PFOM increased by 546.8%. Moreover, the reverse leakage current of the device with the FP and NIET structure decreased by three orders of magnitude. The TCAD simulation revealed that the peak electric field at the interface decreased from 7 MV/cm @ -500 V to 4.18 MV/cm @ -1000 V. These results demonstrate the great potential for the β-Ga2O3 SBD with a FP and NIET structure in power electronic applications.

Electrical Properties of Ga2O3 Schottky Barrier Diodes with and without Mesa Structure

Devices based on wide bandgap (WBG) semiconductors like silicon carbide (SiC), gallium nitride (GaN), and gallium oxide (Ga2O3) are ideal for high-power electronics in harsh environments. Among the WBG semiconductors, ultrawide bandgap (UWBG) β-phase gallium oxide (Ga2O3), EG ≈ 4.8 eV, is emerging as a replacement for the current commercially available wide bandgap (WBG) power electronics due to its generational improvements in performance and manufacturing cost [1]. Ga2O3 has a high theoretical breakdown electrical field of 8 MV/cm which in turn gives its Baliga’s figure of merit for power devices that is larger than other WBG materials. The availability of high-quality Ga2O3 substrates produced from melt-grown bulk single crystals also facilitates the development of vertical power devices.In the current stage, the vertical Schottky barrier diode (SBD) with Ga2O3 can have an improved current spreading effect when compared to power diode devices from Si, SiC, and GaN. Especially, the Ga2O3 is expected to surpass the trade-off relationship between breakdown voltage (BV) and on resistance (Ron,sp) that other materials have [2]. Nevertheless, the Ga2O3 vertical SBD still cannot achieve the theoretical breakdown electric field. One of the key topics for WBG semiconductors application is a structure for improved electrical management such as field rings, junction termination extension, and field plates to reduce the leakage current in the reverse bias state.Here, we investigate the characteristics of Ga2O3 SBDs with and without mesa structure in extreme environments at high and low temperature. Conventional and mesa Ga2O3 SBDs were fabricated on the halide vapor phase epitaxy (HVPE) grown β-Ga2O3 (001). A Sn-doped substrate with 61016 cm-3 was used for the HVPE growth. In the SBD with mesa structure, the circular mesa with a diameter of 162 μm and a depth of 500 nm was formed around anode electrodes. The Ti/Au metal stack on the back side of the substrate acted as a cathode and the anode electrode deposited Ni/Au/Pt layers. After the fabrication process, current-voltage (I-V) measurements were performed on the SBDs between -5 V and 1 V. From the results, the values of Ron,sp at 0.7 V are 46.4 Ω•cm2 and 46.2 Ω•cm2 in conventional and mesa SBDs, respectively. And additionally, the leakage current at -5 V is reduced by approximately 44.3% in the mesa structure. To obtain the Schottky barrier height (SBH) from I-V and capacitance-voltage (C-V) measurements, the C-V was observed in the range of -5 V to 0.5 V at 100 kHz. The SBH values from I-V and C-V measurements, the mesa SBDs have 1% - 5% larger SBH compared to the conventional structure, and it could be related to lower leakage current. Moreover, the depletion depths of conventional and mesa SBDs were 52.2 nm and 57.8 nm, respectively, from C-V measurements. For considering the electrical characteristics in extreme temperatures, the I-V measurements of both SBDs structure will be measured between 75 K to 525 K. From an initial low temperature measurement series, we determine a Richardson constant of 49 A/cm2 comparable to what has been reported by other groups. Furthermore, we will extend the study by performing deep-level transient spectroscopy (DLTS) to understand the defect information in Ga2O3.

2.5 kV Vertical Ga2O3 Schottky Rectifier With Graded Junction Termination Extension

This work demonstrates vertical Ga2O3 Schottky barrier diodes (SBDs) with a novel junction termination extension (JTE) comprising multiple layers of sputtered p-type nickel oxide (NiO). The NiO layers have the varied lengths to enable a graded decrease in effective charge density away from the main junction. The fabrication of this JTE obviates the etch or implantation and shows good throughput. The fabricated Ga2O3 SBDs exhibit a forward voltage below 1.9 V at the current density of 100 A/cm2, a differential specific on-resistance of 5.9 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\text{m}\Omega \cdot $ </tex-math></inline-formula> cm2, and a breakdown voltage over 2.5 kV. The Baliga’s figure of merit (FOM) exceeds 1 GW/cm2 and is among the highest in multi-kilovolt Ga2O3 SBDs. Besides, the capacitance of the JTE region is extracted, allowing for evaluation of the capacitance, charge, and switching FOM of 1.7 kV-class Ga2O3 SBDs with varied current ratings. The results show good promise of Ga2O3 SBDs for kilovolt power electronics.

Leakage current reduction in β-Ga2O3 Schottky barrier diode with p-NiOx guard ring

A β-Ga2O3 Schottky barrier diode (SBD) with a p-type NiOx guard ring was fabricated, and the reverse leakage and subthreshold leakage current reduction was found at high temperatures from temperature-dependent I–V characteristics. The functional mechanisms of NiOx as edge termination on leakage reduction were studied. NiOx can increase the barrier height and passivate the defects at the interface, resulting in the suppression of subthreshold leakage and elimination of current crowding effect confirmed by a thermal emission microscope. From the temperature-dependent x-ray photoelectron spectroscopy characteristics, more holes generated to deplete Ga2O3 at higher temperatures were found. It leads to reduce the reverse leakage current. The small-polaron transportation in NiOx is proposed to argue the implausibility of the leakage conduction in NiOx. This work will offer critical physical insight and a valuable route for developing low-leakage Ga2O3 SBDs.

β -Ga2O3 Schottky barrier diodes with 4.1 MV/cm field strength by deep plasma etching field-termination

In this work, we demonstrate a deep mesa etch design for efficient edge field termination in β-Ga2O3 Schottky barrier diodes (SBDs). The proposed design enabled parallel plate fields higher than 4.1 MV/cm with negligible change to the device ON characteristics. The effect of BCl3/Cl2-based dry etch on (100) and (010) etched vertical sidewalls is also analyzed. A remarkable anisotropy in depletion was observed for etch along (100) and (010) sidewalls. This work provides insight into the impact of etching on n-type Ga2O3 and shows a promising method to realize efficient field termination for high breakdown field strength SBDs.

Vertical β-Ga2O3 Schottky barrier diodes with trench staircase field plate

This study presents vertical Ga2O3 Schottky barrier diodes (SBDs) with a staircase field plate on a deep trench filled with SiO2. It was clarified from device simulation that at high reverse voltage operation, the staircase field plate and the deep trench can effectively alleviate electric field concentration in the Ga2O3 drift layer and the SiO2 layer, respectively. The Ga2O3 SBDs successfully demonstrated superior device characteristics typified by an on-resistance of 7.6 mΩ cm2 and an off-state breakdown voltage of 1.66 kV. These results offer the availability of the trench staircase field plate as an edge termination structure for the development of Ga2O3 SBDs.

Low density of interface trap states and temperature dependence study of Ga2O3 Schottky barrier diode with p-NiOx termination

This work acquires a vertical β-Ga2O3 Schottky barrier diode (SBD) with the advanced termination structure of p-type NiOx and n-type β-Ga2O3 heterojunctions and coupled field plate structures to alleviate the crowding electric field. A Ga2O3 SBD delivers an average breakdown voltage of 1860 V and a specific on-resistance of 3.12 mΩ cm2, yielding a state-of-the-art direct-current Baliga's power figure of merit of 1.11 GW/cm2 at an anode area of 2.83 × 10−5 cm2. In addition, the Ga2O3 SBD with the same fabrication process at a large area of 1.21 × 10−2 cm2 also presents a high forward current of 7.13 A, a breakdown voltage of 1260 V, and a power figure-of-merit of 235 MW/cm2. According to dynamic pulse switching and capacitance-frequency characteristics, an optimized p-NiOx/Ga2O3 interface with a maximum trap density of 4.13 × 1010 eV−1 cm−2 is delivered. Moreover, based on the forward current-voltage measurement at various temperatures, the physics behind a forward conduction mechanism is illustrated. Ga2O3 SBDs with p-NiOx/n-Ga2O3 heterojunction termination, field plate, high power figure of merit, and high quality interface as well as suppressed resistance increase after dynamic pulse switching, verifying their great promise for future high power applications.

Enhancing Breakdown Voltage of a Ga2O3 Schottky Barrier Diode with Small-Angle Beveled and High-k Oxide Field Plate

To increase their breakdown voltage, Ga2O3 Schottky barrier diodes (SBDs) with a beveled field plate were designed based on TCAD platform simulations. The small-angle beveled field plate can effectively alleviate the electric field concentration effect. The breakdown voltage of Ga2O3 SBDs can reach 1217 V with the SiO2 dielectric and a small-angle (1°) beveled field plate. However, the breakdown mechanism is the early breakdown of the dielectric layer. TO further increase the breakdown voltage, the replacement of SiO2 with a high-k dielectric (Al2O3 and HfO2) can transfer the breakdown location into the Ga2O3 drift layer. By combining the beveled small-angle design and the high-k dielectric, the device demonstrates a Baliga’s figure of merit of 2.94 GW cm−2 and breakdown voltage of 3108 V.

(Invited) How to Achieve Low Thermal Resistance and High Electrothermal Ruggedness in Ga2O3 Devices?

Ultra-wide-bandgap semiconductor gallium oxide (Ga2O3) has been promoted for years as a promising candidate for power electronics and RF applications, due to its high critical electrical field, controllable n-type doping, and the availability of large-diameter wafers by the melt growth. However, a fundamental limitation of Ga2O3 is its low thermal conductivity (k T = 0.1-0.3 Wcm-1K-1), which is about 1/6 of the k T of Si, 1/10 of GaN, and 1/20 of SiC. The resulting high thermal resistance of Ga2O3 chip has brought serious concerns regarding the current and power scalability of Ga2O3 devices and their electrothermal ruggedness. As a result, questions have persisted on the true viability of Ga2O3 devices in industrial power and RF applications.Despite some simulation and modeling works on the Ga2O3 thermal management, there has been no experimental report on the packaging and thermal management of large-area Ga2O3 devices. The lack of these data makes it difficult to compare Ga2O3 with commercial device technologies (e.g., Si, SiC, GaN) and evaluate the application space of Ga2O3 devices. Some recent works characterized the channel (or junction) temperatures in Ga2O3 devices, but all of these devices have small areas with a current much lower than 1 Amp, and none of these devices are packaged.This work presents the first experimental demonstration of large-area Ga2O3 devices and their thermal management through device-package co-optimization. Vertical Ga2O3 Schottky barrier diodes (SBDs) with a 3×3 mm2 Schottky contact area were fabricated with an on/off ratio over 1010, a forward current over 20 A, and a reverse breakdown voltage over 600 V. These large-area Ga2O3 SBDs were packaged in the bottom-side-cooling and double-side-cooling configurations using the nanosilver sintering as the die attach and the silver plate as the thermal pad.Surge current ruggedness is an essential ruggedness metric listed in any power diode’s datasheet and the most important indicator of a device’s transient electrothermal ruggedness. It measures the device’s capability of temporarily sustaining a current much higher than the rated current. To evaluate the surge current ruggedness of packaged Ga2O3 devices, a surge-current test circuit was prototyped to produce a 10-ms-wide half-sinusoidal current waveform based on the JEDEC standard. The surge-current tests revealed a critical surge current of 37.5 A for the single-side-packaged Ga2O3 SBD and 68 A for the double-side-packaged Ga2O3 SBD. The ratio between the peak surge current and the rated current of the double-side-packaged Ga2O3 SBD was found to be superior to that of similarly-rated commercial SBDs.The key enabling mechanisms for this superior-to-SiC surge current capability are two-fold: first, the fabricated Ga2O3 SBD shows a smaller temperature dependence of on-resistance as compared to the SiC SBDs, which strongly reduces the thermal runaway; second, the double-side-packaging allows the heat to be extracted directly from the Schottky junction without the need for going through the low-k T bulk Ga2O3 chip.To further evaluate the steady-state thermal performance of these Ga2O3 SBDs, the junction-to-case thermal resistance (R θJC) of a double-side-packaged Ga2O3 SBD was measured in the bottom-side- and junction-side-cooling configurations. The R θJC characterization is based on the transient dual interface method, i.e., JEDEC 51-14 standard. The R θJC of the junction- and bottom-cooled Ga2O3 SBD was measured to be 0.5 K/W and 1.43 K/W, respectively, with the former R θJC lower than that of similarly-rated commercial SiC SBDs. This low R θJC is attributable to the heat extraction directly from the Schottky junction instead of through the Ga2O3 chip.The higher surge current ruggedness and lower thermal resistance demonstrated in a large-area, packaged Ga2O3 SBD as compared to the similarly-rated SiC devices proves the viability of Ga2O3 devices for high-power applications. Note that no complex or costly process, such as substrate thinning and layer transfer, has been applied to our Ga2O3 chip. These results manifest that device-packaging co-optimization is an effective and low-cost approach for the thermal management of Ga2O3 devices.

Characterization of thermal-resistance in Ga2O3 Schottky barrier diodes with temperature-sensitive electrical parameters

The temperature and thermal resistance of Ga2O3 Schottky barrier diodes were investigated using electrical methods with temperature-sensitive electrical parameters and the structure function method. The analysis was based on the voltage of the Schottky junction as a temperature-sensitive parameter so as to measure the junction temperature of Ga2O3 Schottky barrier diodes. The junction-case thermal resistance of the Ga2O3 Schottky barrier diodes was accurately extracted by the transient dual interface test method to be 39.04 °C W−1, which increased slightly with the increase of power current. In addition, the temperature extracted with the electrical method was compared with the result of infrared measurements, which indicated that the temperature extracted with the infrared was significantly higher than the result of the electrical method. This difference can be explained in that the temperature extracted by the electrical method was the temperature of the active region of the device, whereas the result of infrared presented the maximum temperature of the device. Furthermore, the low thermal conductivity of Ga2O3 resulted in temperature inhomogeneity on the device surface and further increased the temperature difference. This study provides a convenient and non-destructive method for rapid measurement of the thermal characteristics of the Ga2O3 Schottky barrier diodes, and enables rapid evaluation of the whole thermal system.

Experimental Study on Static and Dynamic Characteristics of Ga2O3 Schottky Barrier Diodes With Compound Termination

In this letter, the ultrafast reverse recovery <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">β</i> -Ga <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> Schottky barrier diode (SBD) with improved breakdown voltage is proposed and investigated experimentally. It features the compound termination, consisting of air space field plate and thermal oxidation terminal. The compound termination not only reduces high-density interface states at the dielectric/Ga <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> interface and the electron concentration in the oxidation terminal, but also modulates the electric-field distribution and suppresses the peak electric-field at the bottom of anode. Therefore, the reverse leakage current is suppressed as well as the reverse recovery and breakdown characteristics are improved effectively. The Ga <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> SBDs with the diameter of 1000 μm obtain ultrashort reverse recovery time of 7.5 ns and ultralow reverse recovery charge of 1.0 nC at <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">di</i> / <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">dt</i> = 50 A/μs with its breakdown voltage up to 400 V, maintaining good rectification characteristics. The temperature-dependences of both forward conduction and reverse recovery characteristics are discussed in temperature range from 300 to 500 K. The results prove that the superior electronics performance of the <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">β</i> -Ga <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> SBDs with good electronics thermal tolerance can overcome the low thermal conductivity of <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">β</i> -Ga <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> to a certain extent. The fabricated <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">β</i> -Ga <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> SBDs have great potential for high power and high-frequency applications.

Fast-response self-powered solar-blind photodetector based on Pt/[formula omitted]-Ga2O3 Schottky barrier diodes

A Schottky barrier diode solar-blind photodetector was fabricated on single crystal β-Ga2O3. Optoelectronic tests at 254 nm have shown that the detector has the maximum ratio (nearly 1 × 104) of light to dark current at zero voltage bias, indicating that the detector can work without any external energy (self-powered action). A fast response speed of the detector has also been found, while the rise and decay time are only 65 ms and 15 ms at self-powered mode, respectively. With increasing the illumination intensity, the photocurrent of the device is enhanced linearly, maintaining the fast response speed. Under a large fixed bias, the photoresponse time turns to be longer comparing with that at zero voltage, which can be attributed to the electrons and holes captured by the oxygen vacancies being released gradually under an applied bias. In addition, the mechanism of this self-powered photodetector has been explained by understanding the motion of photo-generated carrier.

Modeling, simulations, and optimizations of gallium oxide on gallium–nitride Schottky barrier diodes

With technology computer-aided design (TCAD) simulation software, we design a new structure of gallium oxide on gallium–nitride Schottky barrier diode (SBD). The parameters of gallium oxide are defined as new material parameters in the material library, and the SBD turn-on and breakdown behavior are simulated. The simulation results reveal that this new structure has a larger turn-on current than Ga2O3 SBD and a larger breakdown voltage than GaN SBD. Also, to solve the lattice mismatch problem in the real epitaxy, we add a ZnO layer as a transition layer. The simulations show that the device still has good properties after adding this layer.

Origin of reverse leakage current path in edge-defined film-fed growth (001) β -Ga2O3 Schottky barrier diodes observed by high-sensitive emission microscopy

We utilized ultra-high sensitive emission microscopy to investigate the origin of reverse leakage current of edge-defined film-fed grown (001) β-Ga2O3 Schottky barrier diodes. In the emission patterns, we observed a partially appearing void, having a typical width and depth of 300 and 83 nm, respectively, with a base angle of 75°, below the Schottky barrier contact on the β-Ga2O3 surface. Simulations show that the electric field at the bottom of the void reached 9 × 106 V/cm at a reverse bias of −60 V and in the case of an ideally flat surface 3.1 × 106 V/cm. This indicates that the reverse leakage current originates from an electric field concentration in the partially appearing voids on the surface. On the other hand, we have confirmed that there is no clear relationship between the leakage current path and the dislocations observed by synchrotron x-ray topography.

In Situ Observation of β-Ga2O3 Schottky Diode Failure Under Forward Biasing Condition

In this article, we investigate defect nucleation leading to device degradation in $\beta $ -Ga2O3 Schottky barrier diodes by operating them inside a transmission electron microscope. Such in situ approach allows simultaneous visualization and quantitative device characterization, not possible with the current art of postmortem microscopy. High current density and associated mechanical and thermal fields are shown to induce different types of crystal defects, from vacancy cluster and stacking fault to microcrack generation prior to failure. These structural defects can act as traps for carrier and cause device failure at high biasing voltage. Fundamental insights on nucleation of these defects and their evolution are important from materials reliability and device design perspectives.

Demonstration of Large-Size Vertical Ga2O3 Schottky Barrier Diodes

Large-size vertical β-Ga <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> Schottky barrier diodes (SBDs) with various device areas were demonstrated on a Si-doped n-type drift layer grown by hydride vapor phase epitaxy (HVPE) on bulk Sn-doped (001) n-type β-Ga <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> substrate. In this letter, the devices have two circular contacts with a diameter of 1500 and 500 μm and two square contacts with dimensions of 1600 × 1600 μm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> and 800 × 800 μm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> , corresponding to the area of 0.2 × 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-2</sup> cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> (the smallest device), 0.6 × 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-2</sup> , 1.8 × 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-2</sup> , and 2.6 × 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-2</sup> cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> (the largest device). The breakdown voltage (BV) was determined to be -261 V for the largest device and -427 V for the smallest device. Also, the ideality factor (η) of vertical Ga <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> SBDs with different device areas exhibited the same value of 1.07, except for the largest device area of 2.6 × 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-2</sup> cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> with an ideality factor of 1.21. At an applied forward bias of VF= 2 V, the specific on-state resistance (RonA) of all the Ga <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> SBDs remains relatively low with values ranging from 1.43 × 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-2</sup> Ω cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> to 7.73 × 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-2</sup> Ω cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> . The measured turn-on voltage (Von) of all the SBDs remains low with a narrow distribution.

Beveled Fluoride Plasma Treatment for Vertical $\beta$ -Ga2O3Schottky Barrier Diode With High Reverse Blocking Voltage and Low Turn-On Voltage

In this letter, we report on demonstrating a high performance vertical $\beta $ -Ga2O3 Schottky barrier diode (SBD) based on a self-aligned beveled fluorine plasma treatment (BFPT) edge termination structure. Owing to the strong electronegativity of fluorine ions, the fixed negative charges introduced by F ions during self-aligned BFPT process alleviate the electric field crowding, reduce the reverse leakage current and improve the breakdown voltage up to 1 050V even with a low differential on resistance of 2.5 $\text{m}\Omega \cdot $ cm2, combining with a high $I_{\text {on}}/I_{\text {off}}$ of 109, a Schottky barrier height of 1.03 eV and a low ideality factor of 1.07-1.11.Without implantation and post annealing, the self-aligned BFPT can serve as a simple, effective and viable edge termination technique to fabricate high performance $\beta $ -Ga2O3 rectifiers.

3.4 kV Breakdown Voltage Ga2O3 Trench Schottky Diode with Optimized Trench Corner Radius

To improve the blocking performance of Ga2O3 Schottky barrier diode (SBD), based on the field strength distribution at the bottom of the trench and edge effect, the impacts of structure parameter on breakdown voltage and the figure of merit (FOM) were investigated by TCAD simulation and optimization. The results indicated that the breakdown voltage raised as the corner radius of trench R and the trench length K increased in a certain range, in which K was employed to optimize the structure with a minor mesa width W. In addition, Al2O3 was confirmed as an appropriate dielectric layer material in Ga2O3 SBD. When the structure parameters were W = 1 μm, R = 0.6 μm, K = 0.8 μm–0.9 μm and Al2O3 was selected as dielectric layer materials, a Ga2O3 trench SBD with breakdown voltage of 3.4 kV and the FOM of over 1.7 GW·cm−2 was proposed.

High-voltage vertical Ga2O3 power rectifiers operational at high temperatures up to 600 K

This work presents the temperature-dependent forward conduction and reverse blocking characteristics of a high-voltage vertical Ga2O3 power rectifier from 300 K to 600 K. Vertical β-Ga2O3 Schottky barrier diodes (SBDs) were fabricated with a bevel-field-plated edge termination, where a beveled sidewall was implemented in both the mesa and the field plate oxide. The Schottky barrier height was found to increase from 1.2 eV to 1.3 eV as the temperature increases from 300 K to 600 K, indicating the existence of barrier height inhomogeneity. The net donor concentration in the drift region shows little dependence on the temperature. The reverse leakage current up to 500 V was found to be limited by both the thermionic-field electron injection at the Schottky contact and the electron hopping via the defect states in the depletion region. At 300–500 K, the leakage is first limited by the electron injection at low voltages and then by the hopping in depleted Ga2O3 at high voltages. At temperatures above 500 K, the thermionic field emission limits the device leakage over the entire voltage range up to 500 V. Compared to the state-of-the-art SiC and GaN SBDs when blocking a similar voltage, our vertical Ga2O3 SBDs are capable of operating at significantly higher temperatures and show a smaller leakage current increase with temperature. This shows the great potential of Ga2O3 SBDs for high-temperature and high-voltage power applications.

High-Voltage ($\overline{\text{2}}01$ ) $\beta$ -Ga2O3 Vertical Schottky Barrier Diode With Thermally-Oxidized Termination

In this letter, a high-performance ( $\overline {{2}} 01$ ) $\beta $ -Ga2O3 vertical Schottky Barrier Diode (SBD) with a thermally oxidized termination is reported. A novel edge termination at the Schottky contact edge is formed by using thermal oxidation treatment, which reduces the electron concentration and effectively suppresses the peak electric field. By using a thermal oxidation termination, the breakdown voltage ( ${V}_{\text {br}}$ ) of $\beta $ -Ga2O3 SBD increases from 380 V to 940 V, and the specific on-resistance ( ${R}_{\text {on,sp}}$ ) just increases from 2.9 $\text{m}\Omega \cdot $ cm2 to 3.0 $\text{m}\Omega \cdot $ cm2. Our device demonstrates a power figure of merit ( ${V}_{\text {br}}^{{2}}/{R}_{\text {on,sp}})$ as high as 295 MW/cm2. These results indicate that the thermally oxidized termination shows a new way to improve the breakdown characteristics of $\beta $ -Ga2O3 SBD.