High Reverse Voltage Research Articles

Single-event burnout in β-Ga2O3 Schottky barrier diode induced by high-energy proton

Single-Event Burnout (SEB) can cause hard damage to devices, leading to permanent failure. However, previous studies have rarely explored the effects of high-energy proton irradiation-induced SEB in β-Ga2O3 Schottky Barrier Diode (SBD), and the underlying mechanisms remain largely unexplored. Experimental results indicate that the reverse bias voltage during irradiation is a critical factor influencing the failure of β-Ga2O3 SBD. Compared to 300 MeV proton irradiation without bias, the introduction of a 300 V reverse bias voltage results in a significant reduction in forward current density (JF). When the reverse bias voltage reaches 400 V or higher, the 300 MeV proton induces SEB in the device. The SEM image of the damaged region reveals that the irradiated device has “voids” formed due to the melting of the Ga2O3 material. Geant 4 and TCAD simulation results indicate that the burnout phenomenon is caused by the elevated lattice temperature inside the device, which results from the implantation of secondary particles under a high reverse bias voltage. As the reverse bias voltage increases, the maximum lattice temperature of β-Ga2O3 SBD also rises. When the reverse bias voltage is sufficiently high, the local lattice temperature inside the device reaches the melting point of Ga2O3 material, ultimately leading to SEB.

Impact of Perovskite Subcell Breakdown on the Performance of Perovskite/Perovskite/Silicon Triple‐Junction Solar Cells

Perovskite‐based triple‐junction solar cells have recently gained significant attention and are rapidly developing, thanks to the insights gained from the advancement in its dual‐junction counterparts. However, employing perovskite materials in multijunction solar cells with more than two junctions brings new challenges that have not yet been addressed. One aspect is the possibility of reverse bias breakdown of perovskite subcells during operation of the triple–junction device. This is more relevant for triple‐junction solar cells because a higher reverse voltage might drop at perovskite subcells compared to the case of dual‐junction solar cells. Herein, the breakdown voltages of the two perovskite subcells in perovskite/perovskite/silicon triple‐junction solar cells are determined by progressively increasing the reverse bias applied to the subcells in a single‐junction architecture during current–voltage measurements and monitoring the appearance of shunts using illuminated lock‐in thermography measurements. Furthermore, to analyze the effect on the final triple–junction solar cell, the triple‐junction device is brought in different current limitation conditions. It is shown that the subcell breakdown can happen during the operation of the triple‐junction solar cell, especially for the case where the perovskite top cell is limiting the overall current of the device. This effect is less severe when the middle perovskite cell limits the current due to the absence of a direct contact with the silver metallization which has shown to be the major degradation site during reverse biasing of perovskite solar cells. Finally, there is no concern regarding breakdown of the silicon bottom cell due to the higher breakdown voltage of silicon compared to perovskite.

Effect of hydrogen treatment on 4H-SiC Schottky barrier diodes

In this letter, 4H-SiC Schottky barrier diodes (SBDs) with Ti Schottky metal have been subjected to hydrogen treatment in a confined environment of 4% H2 and 96% N2 at 150 °C. The effect of hydrogen treatment on the SBDs electrical characteristics has been investigated by technical computer-aided design simulation (TCAD) and power device analyzer curve tracer. The change of electrical parameters of SBDs measured after hydrogen treatment is studied in detail, and the related degradation mechanism is discussed. It was found that hydrogen treatment affected both the interface region and bulk region of SiC SBDs. After hydrogen treatment, the Schottky barrier increases slightly, the ideal factor (n) decreases slightly, and the interfacial state density (D it) decreases. Hydrogen treatment resulted in a slight reduction in specific on-resistance (R on-sp), which was attributed to the diffusion of H in SBDs. Through TCAD simulation, it is determined that the diffusion of H in the body diode of SBDs is the main reason for the degradation of high forward current and high reverse voltage characteristics.

Analysis of photodiode and barrier properties of CoPc/n-Ge heterojunction under various illumination wavelengths

The present investigation reports the analysis of barrier parameters of the CoPc/n-Ge heterojunction photodiode under varied illumination wavelengths from 500 nm to 1200 nm in steps of 25 nm. The efficiency of this photodiode was also summarized using responsivity, detectivity and quantum efficiency for different illumination wavelengths. The photocurrent seems to be maximum for 850 nm and 1175 nm and shows higher responsivity of 1.72 A/W and 2.38 A/W at 775 nm and 1125 nm wavelength respectively. The quantum efficiency of the photodiode was found to be 275 % at illumination wavelength of 775 nm and 263 % at 1125 nm. For the selective illumination wavelengths (775 nm, 850 nm, 1125 nm and 1175 nm), the electrical properties of the CoPc/n-Ge photodiode were studied. Noticeable variation in the barrier parameters of the photodiode is observed with illumination than compared to dark. Significantly, the series resistance was found to be decreased and shunt resistance is increased with illumination wavelength than compared to dark. Current conduction mechanisms were also investigated in both the forward and reverse bias of the photodiode. The forward current transport processes show that at moderately high bias the current conduction might be associated with TCLC. It is also evidenced from the reverse conduction mechanism that at low reverse voltages PFE is found to be dominant whereas SE is dominant at high reverse voltages. The reduced interface state densities at the CoPc/n-Ge interface were observed under illumination than compared to dark.

Breadboard of Microchip and Avalanche Photodiode in Linear and Geiger Mode for LiDAR Applications

This paper reports the implementation of two critical technologies used in LiDARs: 1) A microchip Q-switched laser breadboard and 2) breadboard of an Indium gallium arsenide avalanche photodiode working at 300 K with high reverse polarization voltages. Microchip Q-switched lasers are small solid state back pumped lasers, that can generate high energy short pulses. The implemented breadboard used an Erbium and Ytterbium co doped phosphate glass, a COMALO crystal with 98% (initial transparency) and an output coupler of 98% reflectivity. For the sensor test, a system for the simultaneous operation in vacuum and wide range of temperatures was developed. Avalanche photodiodes are reverse polarized photodiodes with high internal gain, due to their multiple layer composition, capable of building up high values of photocurrent from small optical signals by exploiting the avalanche breakdown effects. The test avalanche photodetector was assembled to be operated in two modes: Linear and Geiger mode, to achieve this behavior, a transimpedance amplifier circuit was implemented. These two technologies are critical for mobile LiDAR applications, due to its low mass and high efficiency. The paper describes the breadboard implementation method and sensor characterization at low temperature and high voltage (beyond breakdown voltage).

Breadboard of Microchip Laser and Avalanche Photodiode in Geiger and Linear Mode for LiDAR Applications

This paper reports the implementation of two critical technologies used in light detection and ranging for space applications: (1) a microchip Q-switched laser breadboard; (2) a breadboard of an indium gallium arsenide avalanche photodiode working at 292 K with high reverse polarization voltages. Microchip Q-switched lasers are small solid-state back-pumped lasers that can generate high-energy short pulses. The implemented breadboard used an erbium and ytterbium co-doped phosphate glass, a Co:Spinel crystal with 98% initial transparency, and an output coupler with 98% reflectivity. For the sensor test, a system for simultaneous operation in vacuum and a wide range of temperatures was developed. Avalanche photodiodes are reverse-polarized photodiodes with high internal gain due to their multiple layer composition, capable of building up high values of photocurrent from small optical signals by exploiting the avalanche breakdown effects. The test avalanche photodetector was assembled to be operated in two modes: linear and Geiger mode. The produced photocurrent was measured by using: (1) a passive quenching circuit; (2) a transimpedance amplifier circuit. These two technologies are important for mobile light detection and ranging applications due to their low mass and high efficiencies. The paper describes the breadboard’s implementation methods and sensor characterization at low and room temperatures with high bias voltages (beyond breakdown voltage).

High speed and broadband fiber-integrated WS2/Bi2O2Se avalanche photodetector

Photodetectors based on two-dimensional(2D) materials have attracted tremendous attention in recent years because of their potential for development in compact and integrated devices. Owing to the high carrier mobility and air stability, the newly discovered 2D bismuth oxyselenide (Bi2O2Se) exhibits outstanding optoelectronic properties. However, the high dark current inevitably restricts the performance of the Bi2O2Se-based photodetectors. Here, we propose and demonstrate a fiber-integrated photodetector with a low dark current of ∼10 −10 A by assembling a WS2/Bi2O2Se Van der Waals heterostructure onto the end-face of a standard optical fiber. Benefiting from the narrow bandgap of the 2D materials, the fiber-integrated photodetector exhibits a broadband detection range from 650 to 1630 nm along with a responsivity of 1.13 AW−1. The fast rise time is measured as ∼410μs, while the fall time is ∼600μs. Taking advantage of the built-in potential in the WS2/Bi2O2Se heterostructure, the photodetector can work on self-powered mode. Applied a certainly high reverse voltage, the WS2/Bi2O2Se fiber-integrated photodetector can operate at avalanche breakdown region with an external quantum efficiency of 141% and an avalanche gain of 44 under the input power of 56.7μW. Finally, the fiber-integrated photodetector is applied to measure the wrist bending owing to its high photoresponsivity. These findings indicate that our proposed device has intriguing capabilities in terms of photodetection and on-line power monitoring, which enable our proposed device to have superb application potential in a fiber-integrated multi-function system.

Freestanding High-Power GaN Multi-Fin Camel Diode Varactors for Wideband Telecom Tunable Filters

The quality, resolution, and quantity of information transmitted in RF front end modules favor compact tunable filters with varactor elements that can handle high power and that are highly linear. Gallium nitride (GaN) varactors can theoretically reach the highest quality factor figure of merit (QFOM), owing to the GaN outstanding breakdown electric field and good electron mobility. Popularly pursued GaN Schottky diode varactors suffer from leakage currents at high reverse voltage biases at their junctions and because of GaN inherent threading dislocations in thin GaN layers on foreign substrates. We devised a novel device architecture to overcome these limitations. First, we employ an interdigitated anti-series multi-Fin camel diode structure composed of a thin <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\text{p}^{+}$ </tex-math></inline-formula> GaN top layer situated between the Schottky metal and an n-type GaN drift layer. The anti-series symmetric Fin structure leads to excellent linearity and minimizes device parasitics to achieve measured record high <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${Q}$ </tex-math></inline-formula> factors. The p-GaN layer raises the barrier height to suppress reverse leakage current to maintain a high <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${Q}$ </tex-math></inline-formula> factor at higher reverse biases than Schottky diodes. Second, we utilize GaN on Qromis Substrate Technology (QST) wafers that permit the growth of thick GaN layers with lower dislocation densities and lower leakage currents than GaN-on-Si and that are comparable to GaN-on-GaN. We report in this work the fabrication and dc, RF <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${S}$ </tex-math></inline-formula> -parameters of these diodes, and assess their potential with empirical models. Breakdown voltage of 146 V and extrapolated <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${Q}$ </tex-math></inline-formula> factor of 84, 33, and 9 at 2, 5, and 18 GHz, respectively, are obtained in multi-Fin back-to-back varactor device configuration.

Performance of neutron-irradiated 4H-silicon carbide diodes subjected to alpha radiation

The unique electrical and material properties of 4H-silicon-carbide (4H-SiC) make it a promising candidate material for high rate particle detectors. In contrast to the ubiquitously used silicon (Si), 4H-SiC offers a higher carrier saturation velocity and larger breakdown voltage, enabling a high intrinsic time resolution and mitigating pile-up effects. Additionally, as radiation hardness requirements grow more demanding in the context of future high luminosity high energy physics experiments, wide-bandgap materials such as 4H-SiC could offer better performance due to low dark currents and higher atomic displacement thresholds. In this work, the detector performance of 50 µm thick 4H-SiC p-in-n planar pad sensors was investigated at room temperature, using an 241Am alpha source at reverse biases of up to 1100 V. Samples subjected to neutron irradiation with fluences of up to 1 × 1016 neq/cm2 were included in the study in order to quantify the radiation hardness properties of 4H-SiC. A calibration of the absolute number of collected charges was performed using a GATE simulation. The obtained results are compared to previously performed UV transient current technique (TCT) studies. Samples exhibit a drop in charge collection efficiency (CCE) with increasing irradiation fluence, partially compensated at high reverse bias voltages far above full depletion voltage. At fluences of 5 × 1014 neq/cm2 and 1 × 1015 neq/cm2, CCEs of 64 % and 51 % are obtained, decreasing to 15 % at 5 × 1015 neq/cm2. A plateau of the collected charges is observed in accordance with the depletion of the volume the alpha particles penetrate for an unirradiated reference detector. For the neutron-irradiated samples, such a plateau only becomes apparent at higher reverse bias, roughly 600 V and 900 V for neutron fluences of 5 × 1014 neq/cm2 and 1 × 1015 neq/cm2. For the highest investigated fluence, CCE behaves almost linearly with increasing reverse bias. Compared to UV-TCT measurements, the reverse bias required to deplete a sensitive volume covering full energy deposition is lower, due to the small penetration depth of the alpha particles. At the highest reverse bias, the measured CCE values agree well with earlier UV-TCT studies, with discrepancies between 1% and 5%.

Technological Causes of p-n-Junction Break-down of Silicon p-i-n Photodiodes

During the manufacture of coordinate quadrant p-i-n photodiodes with a high reverse bias voltage Ubias≥200 V, it was observed the presence of a systematic lack of products at the level of the dark current of one (rarely several) photosensitive element. After measuring the volt-ampere characteristics, it was seen that the cause of this is a breakdown of the p-n junction. Effective methods of increasing the breakdown voltage are reducing the specific resistance of the silicon used, increasing the thickness of the substrate and the depth of the p-n junctions, reducing the concentration of alloying impurities, but these methods should be used in cases that allow the degradation of the relevant parameters to be neglected. In particular, it is necessary to provide a level of technology that reduces the probability of a breakdown. A number of technological factors that can be the reasons for reducing the breakdown voltage of the p-n junction have been established and investigated. Strong influence on the breakdown voltage. have crystallographic defects, in particular dislocations falling into the region of the p-n junction. By reducing the concentration of alloying impurities, it is possible to significantly reduce the density of dislocations with a small increase in the levels of dark currents. This helps to eliminate the probability of a breakdown. After operations of sprinkling chrome-gold on the reverse side of such a substrate, the appearance of breakdowns was detected. The cause of which are defects formed as a result of local melting of silicon when gold "droplets" with a temperature higher than the melting temperature of silicon fall on it, as a result of boiling in the evaporator. Іt is possible to reduce the probability of the appearance of these defects by spraying from closed evaporators or by increasing the etchability of spraying on the damper. During photolithography, in particular, when etching windows in the oxide, etching wedges are formed, which direct the output of the p-n junction to the surface at an acute angle. These areas are places with an increased level of electric field intensity, respectively, places of probable localization of the breakdown. This can be avoided by using photoresists that provide minimal etching wedges. Irregularities between the oxide windows can also lead to a decrease in the probo voltage, the probability of this can be reduced by careful control of the development and exposure operations and the use of defect-free templates. Another reason for a breakdown can be a violation of the p-n junction due to welding of the contact terminals. In this case, it is a thermal breakdown. This can be avoided by increasing the size of the contact pads with their expansion on silicon oxide, accordingly, welding on the surface of the oxide reduces the probability of a hole. Another method is a local increase in the depth of the p-n junction, but in this case additional technological operations must be carried out.

A Self‐Powered CNT–Si Photodetector with Tuneable Photocurrent

AbstractA photodetector with bias‐tuneable current is realized by adding a film of single‐walled carbon nanotubes (CNT), forming a CNT/Si3N4/Si capacitor, to a prefabricated Pt–Ti/Si3N4/Si metal–insulator–semiconductor (MIS) diode. Electrical characterization of the entire device is performed to extract the temperature‐dependent ideality factor and Schottky barrier height in the framework of the thermionic emission theory. The CNT/Si3N4/Si capacitor increases the reverse current of the parallel Pt–Ti/Si3N4/Si MIS diode by adding a Fowler–Nordheim tunneling current at high reverse voltage bias. This feature endows the photodetector with two different photocurrent levels, photoresponsivity up to 370 mA W−1 and external quantum efficiency up to 50% at 950 nm wavelength. The device also shows a different photoresponse when light is focused on the CNT/Si3N4/Si region or around the Pt–Ti/Si3N4/Si structure. The photodetector can also be used as an optoelectronic Boolean logic device, in which the applied voltage bias and the incident light are the two input signals, and the photocurrent is the output. Furthermore, light generates a photocurrent at zero voltage and a photovoltage at zero current, making the device a self‐powered photodetector.

FEM-based analysis of avalanche ruggedness of high voltage SiC Merged-PiN-Schottky and Junction-Barrier-Schottky diodes

Through comprehensive experimental measurements and TCAD simulation, it is shown that the avalanche ruggedness of SiC MPS & JBS diodes outperforms that of closely rated Silicon PiN diodes taking advantage of the wide-bandgap properties of SiC which leads to a high ionization and activation energy given the strong covalent bonds. Although the MPS diode structure favours a high reverse blocking voltage with small leakage current and a high current conduction, the localise current crowding caused by the multiple P+ implanted region leads to the avalanche breakdown at lower load currents than the SiC JBS diode. The results of Silvaco TCAD Finite Element modellings have a good agreement with the experimental measurements, indicating that SiC JBS diode can withstand the high junction temperature induced by avalanche in line with the calculated avalanche energy.

Reverse gate leakage mechanism of AlGaN/GaN HEMTs with Au-free gate

The reverse gate leakage mechanism of W-gate and TiN-gate AlGaN/GaN high-electron-mobility transistors (HEMTs) with N2 plasma surface treatment is investigated using current–voltage (I–V) and capacitance–voltage (C–V) characteristics and theoretical calculation analysis. It is found that the main reverse gate leakage mechanism of both devices is the trap-assisted tunneling (TAT) mechanism in the entire reverse bias region (–30 V to 0 V). It is also found that the reverse gate leakage current of the W-gate AlGaN/GaN HEMTs is smaller than that of the TiN gate at high reverse gate bias voltage. Moreover, the activation energies of the extracted W-gate and TiN-gate AlGaN/GaN HEMTs are 0.0551 eV–0.127 eV and 0.112 eV–0.201 eV, respectively.

A High Reverse Breakdown Voltage p-GaN Gate HEMT with Field Control Drain

In this work, a high reverse blocking voltage (BV R) p-GaN gate high electron mobility transistor with field control drain (FCD-HEMT) has been proposed and fabricated. The FCD-HEMT features the field control drain (FCD), consisting of electrically shorted Ohmic contact structure and p-GaN cap. In the OFF-state, the 2-Dimensional Electron Gas (2DEG) channel is cut off due to the p-GaN cap introduced field control, which provides FCD-HEMT with reverse blocking capability. In the ON-state, the re-formed 2DEG channel offers a non-potential barrier pathway for electrons transfer from source to drain and ensures a low resistance of the FCD-HEMT. The fabricated device exhibits 1400 V forward breakdown voltage (BV F) and −1240 V reverse breakdown voltage (BV R), 12.7 mΩ·cm2 low specific ON-resistance, and 188 mA mm−1 max drain current while maintaining normally-OFF capability. These results demonstrate the great potential of FCD-HEMTs in 1200 V-class power applications.

Fast neutron irradiation effects on Si- and GaN-based avalanche photodiodes

We report the behaviour of the dark current and gain characteristics of Si- and GaN-based avalanche photodiodes (APDs) irradiated by fast neutrons. For Si-based APDs, the dark current increases with the increase of neutron fluence, indicating that the avalanche property has been seriously affected. The gain values of Si-based APD slightly increase after irradiation by a low neutron fluence of 1.0 × 1012 cm−2, while the device exhibits gain degradation as the fluence increases to 1.0 × 1013 cm−2 or even above at high reverse bias voltage, unlike the previous studies where only degradation was observed. The steep increase of dark current and gain when approaching the breakdown voltage after neutron irradiation indicate that the avalanche property is almost unaffected for GaN-based APDs. Furthermore, we infer that the optical absorption between acceptor state and conduction band in the p-type layer plays an important role in influencing the change of dark current and gain at high reverse bias voltage. The findings not only enrich the understanding of neutron irradiation effect on Si- and GaN-based APDs, but also experimentally prove that GaN-based APDs hold better radiation resistance than Si-based devices.

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.

Optimization of Schottky-contact process on 4H-SiC Junction Barrier Schottky (JBS) Diodes

SiC Junction Barrier Schottky (JBS) Rectifier is a kind of unipolar power diode with low threshold voltage and high reverse blocking voltage. And the Schottky barrier Φ BN is a main technology parameter, which could greatly affect the forward conduction power and reverse leakage current in the JBS rectifiers. Therefore, it is necessary to balance the influence of Φ BN on the electrical characteristics of JBS rectifiers. In this paper, physical properties at the metal-semiconductor at the Schottky-contact could be optimized by the improvement of Schottky-contact process. And this optimization could significantly decrease Φ BN to reduce the on-state voltage drop V F and minimize negative impact on its reverse characteristics. After the completion of Silicon carbide JBS diodes, the static parameter electrical test was carried out on the wafer by using Keysight B1505A Power Device Analyzer/Curve Tracer. The test results show that the Schottky barrier height Φ BN of JBS Schottky rectifier manufactured by the modified Schottky foundation technology decreased from 1.19eV to 0.99eV and I R increased from 1.08μA to 3.73μA (reverse blocking voltage V R=1200V). It indicated that the power consumption of Schottky barrier junction in JBS rectifiers could be significantly reduced by about 25%, and I R could effectively be limited to less than 10μA.

Novel Method of Rebound Tailing Pulse (RTP) for Water Dissociation

Simple low-temperature pulsed power dissociation method for high resistive liquid is proposed in this article. Active high voltage rebound tailing pulse (RTP) diodes are adopted to conventional high voltage pulse power sources. In order to explain this method, the study was performed using deionized water (DIW) (high resistive $>17~\text{M}\Omega \cdot $ cm) electrolysis with two immersed electrodes. The forward pulses, the full-width at half-maximum (FWHM) of 400 ns and forward voltage (7 kV) with rising-up ratio ( dV/dt ) of 1011 V/s, were applied to the electrodes. When a 5 kV RTP diode was simply adopted to this electrical circuit and DIW load in series, the high forward voltage pulse and continuous high reverse current were applied to this circuit. Then, H2 was generated at the anode electrode and OH radical (OH) in the water vessel. Those phenomena were apparently dependent on the anode electrode area. At the beginning of the forwarded high voltage application, the circuit behaved as capacitance load with generated ions and built up charges at the interface between DIW and the electrode. Continuous rebounded high reverse voltage and highly built-up reverse recovery charges induce avalanche breakdown of RTP diode. The rebounded electrical current was found to be collected in the circuit, accompanied by the generation of hydrogen and OH, as well as the tailing current flowing at the interface as a resistive load. In consequence, we point out that rebounded electrons injected from the surrounding water to the anode electrode interface induced the water electrolysis characteristically, according to RTP-diode inserted in the circuit.

Temperature dependent performance of ITO Schottky contacts on β-Ga2O3

Sputtered indium tin oxide (ITO) was used as a rectifying contact on lightly n-type (n ∼ 1016 cm−3) β-Ga2O3 and found to exhibit excellent Schottky characteristics up to 500 K, with no thermally driven degradation to this temperature. The barrier height extracted from current–voltage characteristics was 1.15 ± 0.04 eV at 300 K and 0.78 ± 0.03 eV at 500 K, with thermionic behavior of charge carriers over the image force lowered Schottky barriers dominating the carrier transport at low temperatures. The breakdown voltages were 246, 185, and 144 V at 300, 400 and 500 K, respectively. At 600 K, the diodes suffered irreversible thermal damage. The diode on/off ratio was &amp;gt;105 for reverse biases up to 100 V. At higher reverse voltage, the current shows an I ∝ Vn relationship with voltage, indicating a trap-assisted space-charge-limited conduction (SCLC) mechanism. We observed this SCLC relation when the reverse voltage was larger than 100 V for 300 and 400 K and at &amp;lt;100 V at 500 K. The ITO can also be used to make Ohmic contacts on heavily doped Ga2O3 suggesting the possibility of completely optically transparent power devices.

Vertical β-Ga2O3 Schottky rectifiers with 750 V reverse breakdown voltage at 600 K

Field-plated vertical Ga2O3 rectifiers were operated up to 600 K with reverse breakdown voltage (V B) of 750 V, 950 V at 500 K and 1460 V at 400 K. The barrier height was 1.3 eV at 300 K and reduced to 0.7 eV at 600 K, with ideality factors of 1.05 ± 0.05 and 2 ± 0.1, respectively at these temperatures. On-state resistance, R ON, was 13 mΩ cm2 at 300 K and 41 mΩ cm2 at 600 K, leading to respective Baliga figures of merit of 151 MW cm−2 (300 K) and 13.9 MW cm−2 (600 K). The on–off ratio was >104 for all temperatures measured. The leakage current showed a good fit to the thermionic field emission model when the reverse voltage was less than 80 V, and it was dominated by the tunneling effect at higher voltage. The transition voltage from thermionic emission to tunneling effect decreased as the temperature increased. At high reverse voltage, a large number of electrons are injected into the drift region, and the current shows an I ∝ Vn relationship with voltage, indicating a trap-assisted space-charge-limited conduction (SCLC) mechanism. We observed this SCLC relation when the reverse voltage was larger than 400 V for 500 and 600 K. The associated trap energies for these two regions were extracted as 0.2 and 0.4 eV, consistent with levels in the gap.