Reverse Leakage Current Research Articles

Study of optical float-zone grown gallium oxide schottky barrier diode

Abstract β−Ga2O3 based lateral Schottky barrier diodes are fabricated using Ni/Au as Schottky contact and Ti/Au as Ohmic contact. The Sn-doped β−Ga2O3 sample is grown by the optical float-zone (OFZ) technique. The effect of trenches, which are used for mesa isolation, on breakdown voltage is investigated. The device shows near-ideal characteristics in terms of built-in potential. The parasitic series and shunt resistances are extracted, and their dependency on temperature is established. Modeling of temperature-dependent reverse leakage current is demonstrated using the thermionic emission (TE) model, Poole-Frenkel (PF) emission model, and Fowler-Nordheim (FN) tunneling mechanism. The procedure to extract relevant parameters is explained in terms of bias and temperature dependency. The combined model shows excellent agreement with experimental data over a wide range of bias and temperature. The maximum electric field of 2.3 MV/cm is achieved.

Microstructural and Current-voltage Characteristics in Mo/HfO2/n‑Si Based Metal-Insulator-Semiconductor (MIS) Diode using Different Methods for Optoelectronic Device Applications

This paper investigates the effect of hafnium dioxide (HfO2) thin film as interlayer between the Mo and n-Si semiconductor on the electrical characteristics of the Mo/n-Si Schottky diode (SD). The X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD) results confirmed that HfO2 films were formed on the n-Si semiconductors. The image from SEM and AFM displays that the deposited HfO2 thin film had a uniform appearance good smoothness of the surface. The smooth surfaces of the insulating layer strongly influence the electrical properties of the diode. The electrical properties of the Mo/HfO2/n-Si metal/insulator/semiconductor (MIS) diode were obtained via current-voltage (I-V) measurements in the voltage range from −3 V to +3 V at room temperature. A better rectifying ability and a reduced reverse leakage current were demonstrated by the MIS diode. The MIS dide's barrier height (Bh) and ideality factor value were calculated to be 0.85 eV and 1.21, respectively. The MIS diode was able to achieve a higher b, which allowed the HfO2 interlayer to change BH. The calculated BH values from the I-V, Hernandez, Cheung, and Norde approaches were comparable to one another, demonstrating their validity and consistency. The MIS diode's forward bias log (I) - log (V) curve demonstrated that it was ohmic in low-voltage regimes and that conduction was space-charge-limited in high-voltage regimes. However, for the MIS diode, the Poole-Frenkel and Schottky emissions are the dominant current conduction mechanisms in the lower and higher bias regions. These outcomes indicate that the HfO2 film can be chosen as dielectric materials in the construction of MIS devices.

Strategically constructed AlGaN doping barriers for efficient deep ultraviolet light-emitting diodes.

Here, we propose a sandwich-like Si-doping scheme (undoped/Si-doped/undoped) in Al0.6Ga0.4N quantum barriers (QBs) to simultaneously promote the optoelectronic performances and reliability of deep ultraviolet light-emitting diodes (DUV-LEDs). Through experimental and numerical analyses, in the case of DUV-LEDs with conventional uniform Si-doping QB structure, severe operation-induced reliability degradation, including the increase of reverse leakage current (IR) and reduction of light output power (LOP), will offset the enhancement of optoelectronic performances as the Si-doping levels increase to an extent, which hinders further development of DUV-LEDs. According to a transmission electron microscope characterization and a numerical simulation, an improved interfacial quality in multiple quantum wells (MQWs) and more uniform carrier distribution within MQWs are demonstrated for our proposed Si-doping structure in comparison to the uniform Si-doping structure. Consequently, the proposed DUV-LED shows superior wall-plug efficiency (4%), IR at -6 V reduced by almost one order of magnitude, and slower LOP degradation after 168-h 100 mA-current-stress operation. This feasible doping scheme provides a promising strategy for the high-efficiency and cost-competitive DUV-LEDs.

3-step field-plated β-Ga2O3 SBDs and HJDs with sub-1 V turn-on and kilo-volt class breakdown

Abstract A unique field termination structure combining a 3-step field-plate with N-ion implantation to enhance the reverse breakdown performance of Pt/β-Ga2O3 schottky diodes (SBDs) and NiO/β-Ga2O3 heterojunction diodes (HJDs) is reported. The fabricated devices showed a low Ron,sp of 6.2 mΩ-cm2 for SBDs and 6.8 mΩ-cm2 for HJDs, respectively. HJDs showed a 0.8V turn-on voltage along with an ideality factor of 1.1 leading to a low effective on-resistance of 18 mΩ-cm2. The devices also showed low reverse leakage current (<1mA/cm2) and a breakdown voltage of ~1.4 kV. These results offer an alternative simpler route for fabricating high-performance kilo-volt class β-Ga2O3 diode.

Performance of 4H–SiC radiation detector after high flux proton and Fe13+ heavy ion beam irradiation

A batch of Schottky diode 4H–SiC detectors was fabricated by using Ni/Au electrodes, which were irradiated by Fe13+ heavy ion beam current with a flux of 1 × 1013 n/cm2 to 4.35 × 1014 n/cm2 in a stepwise increment, the forward and reverse I–V characteristics before and after irradiation as well as the energy resolution of α particles produced by 241Am source were tested and compared. The test results show that the reverse leakage current of the 4H–SiC detector that we made after the radiation of Fe13+ heavy ion beam increases gradually with the increase of the irradiation flux, Schottky Barrier Height decreases continuously where the ideal factor gradually increases. When the flux is 4 × 1013 n/cm2, it has risen to 9 μA, but the detector still has an energy resolution of 2.63%. When the flux of Fe13+ heavy ion beam is increased to 8 × 1013 n/cm2, the very obvious degradation phenomenon appears, the Charge Collection Efficiency(CCE) is reduced from 100% to 66.08%, the energy resolution is changed from 1.6% to 4.33%. When flux is increased to 1.4 × 1014 n/cm2, and the detector's performance has degraded seriously, in which the energy resolution is decreased from 1.76% to 9.54%, meanwhile the CCE is reduced from 100% to 64.84%, but it can still be used. As the beam flux reaches 2 × 1014 n/cm2, the detector has been completely damaged. At the same time, the ability of the detector to be resist mixed ion beam irradiation was tested. The 4H–SiC detector still has an energy resolution of 2.51% after receiving a dose of irradiation, which concluded with 1 × 1017 n/cm2 protons and 2 × 1013 n/cm2 Fe13+ heavy ion beams.

Current transport mechanism of lateral Schottky barrier diodes on β-Ga2O3/SiC structure with atomic level interface

Heterogeneous integration of β-Ga2O3 on highly thermal conductive SiC substrate by the ion-cutting technique is an effective solution to break the heat-dissipation bottleneck of β-Ga2O3 power electronics. In order to acquire high-quality β-Ga2O3 materials on SiC substrates, it is essential to understand the influence of the ion-cutting process on the current transport in β-Ga2O3 devices and to further optimize the electrical characteristics of the exfoliated β-Ga2O3 materials. In this work, the high quality of β-Ga2O3/SiC structure was constructed by the ion-cutting process, in which an amorphous layer of only 1.2 nm was formed between β-Ga2O3 and SiC. The current transport characteristics of Au/Pt/Ni/β-Ga2O3 Schottky barrier diodes (SBDs) on SiC were systematically investigated. β-Ga2O3 SBDs with a high rectification ratio of 108 were realized on a heterogeneous β-Ga2O3 on-SiC (GaOSiC) substrate. The net carrier concentration of the β-Ga2O3 thin film for GaOSiC substrate was down to about 8% leading to a significantly higher resistivity, compared to the β-Ga2O3 donor wafer, which is attributed to the increase in acceptor-type implantation defects during the ion-cutting process. Furthermore, temperature-dependent current–voltage characteristics suggested that the reverse leakage current was limited by the thermionic emission at a low electric field, while at a high electric field, it was dominated by the Poole–Frenkel emission from E3 deep donors caused by the implantation-induced GaO antisite defects. These results would advance the development of β-Ga2O3 power devices on high thermal conductivity substrate fabricated by ion-cutting technique.

High-Performance N-Polar GaN/AlGaN Metal–Insulator–Semiconductor High-Electron-Mobility Transistors with Low Surface Roughness Enabled by Chemical–Mechanical-Polishing-Incorporated Layer Transfer Technology

High-Performance N-Polar GaN/AlGaN Metal–Insulator–Semiconductor High-Electron-Mobility Transistors with Low Surface Roughness Enabled by Chemical–Mechanical-Polishing-Incorporated Layer Transfer Technology

Post-trench restoration for vertical GaN power devices

The impact of the post-trench restoration on the electrical characteristics of vertical GaN power devices is systematically investigated in this work. Following the achievement of microtrench-free GaN trench structure with modified dry etching conditions, the post-trench tetramethylammonium hydroxide (TMAH)-based wet etching and UV/Ozone-based oxidation process are employed to further refine the trench profile. It is shown that the c-plane trench bottom is restored to the level of unetched surface, as evidenced by the improved Schottky interface. Additionally, the post-trench treatment exhibits the anisotropic characteristics with the preferred rounded corner profile on m-plane sidewall compared to a-plane sidewall. The simulations and experimental results demonstrate that the trench MOS barrier Schottky (TMBS) rectifier based on m-plane sidewall could suppress the electric field crowding at the trench corner and, hence, reduce the reverse leakage current by 1–2 orders of magnitude. Furthermore, the MOSCAP test structures were fabricated on the trenches. The extracted interface trap density (Dit) confirms the effective restoration of trench bottom. However, the sidewall surface exhibits the relatively large Dit, which emphasizes the necessity of optimizing the sidewall, particularly for devices incorporating sidewall channel. The demonstrated post-trench restoration technique improves the surface quality and trench structure for the significantly enhanced electrical performances, which is essential for the development of vertical GaN power devices.

Comprehensive experimental study on Schottky contact super barrier rectifier

In this paper, on the basis of further discussion of the device structure and operational mechanism of the Schottky contact Super Barrier Rectifier (SSBR), more key experimental results and comparative analysis are added. The experimental results and discussion of the influence of Schottky contact barrier, supper barrier, key cellular parameters and epitaxial layer on device performance are proposed. Both the Schottky contact and super barrier significantly affect forward voltages and reverse leakage currents. However, the influence of the two on forward I–V characteristics is different. The forward voltage and reverse leakage of SSBR have obvious stability as the temperature increases from 20 °C to 150 °C when compared to conventional Schottky Barrier Diode (SBD). Moreover, the forward voltage at small forward current density and high temperature leakage have obvious advantages.

Wet chemical poly-Si(n) wrap-around removal for TOPCon solar cells

This work gives an overview on different technological solutions for polysilicon removal in industrial tunnel oxide passivated contact (i-TOPCon) n-type silicon solar cell fabrication. The removal of parasitically deposited poly-Si layers on the front and the edges is a mandatory requirement for a low reverse bias junction leakage current (Irev). A polysilicon removal study on wafer level shows (i) that the efficient removal of the surface oxide layer before poly-Si etching is crucial to achieve short etching times and (ii) that an additive in the KOH solution enhances etching selectivity between poly-Si and silicon oxide surfaces. To evaluate the impact on device level, TOPCon cells have been fabricated in parallel using in-situ n-doped PECVD and LPCVD layers, as well as ex-situ LPCVD poly-Si layers, with another variation of poly-Si removal processes, namely wet chemical inline, wet chemical batch cluster and atmospheric dry etching (ADE). Our results show that a two-minute inline polysilicon removal in hot KOH meets the Irev qualification in case of as deposited in-situ doped layers, whereas for ex-situ doped layers a batch process with a five-minute KOH etching time is needed. LPCVD poly-Si cells show efficiencies above 23%, PECVD poly-Si cells with a batch cluster poly-Si removal process up to 23.4%.

(Invited) In-Situ MOCVD Etching of GaN Using XeF2 for Selective-Area-Epitaxial-Regrowth of p-Type GaN for High Voltage PN Diodes

PN diodes with multi-kilovolt breakdown voltages have been demonstrated to great than 6 kV in GaN, validating the device potential predicted by the intrinsic material properties of III-nitride semiconductors. However, power control circuits also require switching transistors such as junction field effect transistors (JFETs) and practical diodes such as merged PIN Schottky (MPS) diodes. Such devices usually employ selective areas of p-type semiconductor surrounded by n-type material and require the formation of PN junctions with low reverse leakage current. Selective-area p-type doping in Si and SiC based power devices is typically achieved using implantation and thermal annealing to form the p-type areas. Ion implantation of Mg in GaN has demonstrated p-type conductivity, but this process requires specialized equipment for the high-pressure and high-temperature activation of Mg dopants. We have investigated selective-area-regrowth (SArG) to epitaxially grow p-type GaN as an alternative to dopant implantation. Successful PN diode formation by SArG requires a process to remove residual crystalline damage resulting from the ex-situ inductively coupled plasma (ICP) etch typically used to form the p-well, as well as a method to remove the elevated level of Si found at the regrowth interface of a surface that had been exposed to air. For the case of SArG of p-GaN on air-exposed, blanket ICP etched n-type GaN, we present the novel use of a fluorine-based precursor (XeF2) for in-situ etching of GaN in the MOCVD chamber. Unlike chlorine (TBCl and CCl4) and bromine (CBr4) -based precursors we have studied; we obtained a smooth surface following in-situ fluorine etching of air-exposed GaN. Schottky barrier diodes (SBDs) formed by shadow mask evaporation on in-situ fluorine etched n-GaN that had been previously ICP etched showed reverse leakage currents to -40 V that are equal to those of SBDs formed on as-grown n-GaN layers. The in-situ fluorine/ICP etched Schottky diodes had reverse leakage currents more than 3 orders of magnitude lower than those formed on n-GaN layers that had only experienced ICP etching. This suggests that the in-situ fluorine etch was effective at removing the residual damage from the ICP etch process. Furthermore, we discuss the use of in-situ fluorine etching to reduce the concentration of Si at the regrowth interface required to form PN junctions with low reverse leakage current. This work was supported in part by the Advanced Research Projects Agency – Energy (ARPA-E), U.S. Department of Energy under the PNDIODES program directed by Dr. Isik Kizilyalli, and in part by the US Department of Energy (DOE) Vehicle Technologies Office (VTO) under the Electric Drive Train Consortium. Sandia National Laboratories is a multimission laboratory managed and operated by National Technology and Engineering Solutions of Sandia, LLC., a wholly owned subsidiary of Honeywell International, Inc., for the U.S. Department of Energy’s National Nuclear Security Administration under contract DE-NA-0003525. The views expressed in the presentation do not necessarily represent the views of the U.S. Department of Energy or the United States Government.

Ultra-low reverse leakage in large area kilo-volt class β-Ga2O3 trench Schottky barrier diode with high-k dielectric RESURF

We introduce vertical Schottky barrier diodes (SBDs) based on β-Ga2O3 with trench architecture, featuring a high-permittivity dielectric RESURF structure. These diodes are designed for application demanding high voltage and current capacities while maintaining ultra-low reverse leakage currents. The trench design plays a pivotal role in reducing the electric field at the metal–semiconductor junction, thereby yielding minimal reverse leakage attributed to field emission under high reverse bias conditions. Additionally, the incorporation of a high-k dielectric helps to suppress leakage through the trench bottom corner dielectric layer. The small area trench SBD (200 × 200 μm2) demonstrates a breakdown voltage exceeding 3 kV, accompanied by a reverse leakage current of less than 1 μA/cm2 at 3 kV. Moving on to larger area devices, the 1 × 1 and 2 × 2 mm2 devices exhibit breakdown voltages of 1.8 and 1.4 kV, while accommodating pulsed forward currents of 3.5 and 15 A, respectively. The capacitance, stored charge, and switching energy of the trench SBDs are also found to be less than the similarly rated commercial SiC SBDs, reinforcing their potential for enhanced switching efficiency.

Vertical β-Ga2O3 metal–insulator–semiconductor diodes with an ultrathin boron nitride interlayer

In this work, we demonstrate the high performance of β-Ga2O3 metal–insulator–semiconductor (MIS) diodes. An ultrathin boron nitride (BN) interlayer is directly grown on the Ga2O3 substrate by pulsed laser deposition. X-ray photoelectron spectroscopy, Raman spectroscopy, and high-resolution transmission electron microscopy confirm the existence of a 2.8 nm BN interlayer. Remarkably, with the insertion of the ultrathin BN layer, the breakdown voltage is improved from 732 V for Ga2O3 Schottky barrier diodes to 1035 V for Ga2O3 MIS diodes owing to the passivated surface-related defects and reduced reverse leakage currents. Our approach shows a promising way to improve the breakdown performance of Ga2O3-based devices for next-generation high-power electronics.

Reverse Blocking Enhancement‐Mode AlGaN/GaN HEMTs with Hybrid p‐GaN Ohmic Drain on the Si Substrates

Hybrid p‐GaN Ohmic drain reverse blocking high electron mobility transistors (RB‐HEMTs) and conventional p‐GaN Enhancement‐mode (E‐mode) HEMTs are designed and fabricated on the Si substrates. Compared with the conventional p‐GaN HEMT, the RB‐HEMT can achieve great reverse blocking capability. The forward and reverse blocking voltages of the RB‐HEMT are 1116 V and 1056 V and the turn‐on voltage of the device is 1.07 V. When the temperature rises from 25 °C to 150 °C, the turn‐on voltage of the RB‐HEMT increases from 1.07V to 1.10 V, and the Vth increases from 1.97V to 2.07 V. The difference in turn‐on voltage and threshold voltage is mainly due to the different metals in contact between the gate and drain electrodes and p‐GaN. The reverse leakage current of the RB‐HEMT is 1.16 × 10−1 mA mm−1 when the temperature is 150 °C, which still keep good reverse blocking ability at high temperatures.

A Wide Input Range All-NMOS Rectifier With Gate Voltage Boosting Technique for Wireless Power Transfer

This brief presents an all-NMOS RF-DC rectifier with a wide high power conversion efficiency (high-PCE) input power range by utilizing gate voltage boosting technique (GVBT). The all-NMOS architecture combines the benefits of crosscoupled and GVBT-based diode-like rectifiers for maximum electron mobility and reduced the conduction losses. The GVBT applied to rectifying transistors not only reduces the reverse leakage current, but also enhances the conductivity. As a result, the PCE and the input power range are improved simultaneously. The proposed rectifier is fabricated with a 0.18-lm standard CMOS technology. The measurement results show that the all-NMOS rectifier achieves 57.6% PCE, -14.8 dBm sensitivity and large than 20 dB high-PCE input power range with a 10 kΩ load.

The effect of Si3N4/Al2O3 stacked structure of AlGaN/GaN HEMTs

Excessive gate leakage current and current collapse effects are the critical reliability issues for GaN-based high electron mobility transistors (HEMTs). In this paper, Si3N4 passivation layers was grown separately on p-GaN gate HRCL-HEMTs with or without Al2O3 film, and the gate leakage and current collapse effects of the devices and their intrinsic mechanisms were investigated. It is found that the device with Si3N4/Al2O3 stacked structure has better performance in terms of gate reverse leakage current, breakdown voltage, etc. The Al2O3 film blocking layer can reduce the H plasma damage to the channel, decrease the gate leakage, and the passivation can effectively suppress the increase of gate leakage current. Through variable temperature characteristic test, it is verified that the dominant mechanism of the device gate reverse leakage current is the two-dimensional variable range hopping (2D-VRH) model. The interface state between Si3N4 passivation layer and Al2O3 film increases the trap activation energy of the device, which is the reason for the reduction of gate reverse leakage current, and also causes the current collapse effect of the device.

Large-Scale β-Ga2O3 Trench MOS-Type Schottky Barrier Diodes with 1.02 Ideality Factor and 0.72 V Turn-On Voltage

β-Ga2O3 Schottky barrier diodes (SBDs) suffer from the electric field crowding and barrier height lowering effect, resulting in a low breakdown voltage (BV) and high reverse leakage current. Here, we developed β-Ga2O3 trench MOS-type Schottky barrier diodes (TMSBDs) on β-Ga2O3 single-crystal substrates with halide vapor phase epitaxial layers based on ultraviolet lithography and dry etching. The 1/C2−V  plots are deflected at 2.24 V, which is caused by the complete depletion in the mesa region of the TMSBDs. A close-to-unity ideality factor of 1.02 and a low turn-on voltage of 0.72 V are obtained. This is due to the low interface trap density in the metal/semiconductor interface of TMSBDs, as confirmed by the current–voltage (I–V) hysteresis measurements. The specific on-resistance calculated with the actual Schottky contact area increases as the area ratio (AR) increases because of the current spreading phenomenon. Furthermore, the reverse leakage current of the TMSBDs is smaller and the BV is increased by 120 V compared with the regular SBD. This work paves the way for further improving the overall performance of β-Ga2O3 TMSBDs.

Correlations between reverse bias leakage current, cathodoluminescence intensity and carbon vacancy observed in 4H-SiC junction barrier Schottky diode

Reverse bias currents of ten commercial junction barrier Schottky diodes were measured, and the dies were studied by scanning electron microscope (SEM) and cathodoluminescence (CL) after the de-capsulation of the diodes. Defect emissions (DEs) of 2.62 eV were observed in all the CL spectra. By comparing the SEM images, the integral CL intensity spatial mappings and the reverse bias leakage currents, correlations between the leakage current, the integral CL intensity and the Al-implantation process were established. The data of reverse bias leakage current against the reverse bias voltage taken at room temperature followed the Poole Frenkel emission from the Z 1/Z 2 carbon vacancy states to the conduction band. The DE at 2.62 eV is associated with the electronic transition from Z 1/Z 2 to the valence band. The current observation also opens up the feasibility of screening off SiC diodes with large leakage current during production by inspecting the CL intensity before the device fabrication is complete.

Design, preparation, and characterization of a novel ZnO/CuO/Al energetic diode with dual functionality: Logic and destruction

Self-destructing chips have promising applications for securing data. This paper proposes a new concept of energetic diodes for the first time, which can be used for self-destructive chips. A simple two-step electrochemical deposition method is used to prepare ZnO/CuO/Al energetic diode, in which N-type ZnO and P-type CuO are constricted to a PN junction. This paper comprehensively discusses the material properties, morphology, semiconductor characteristics, and exploding performances of the energetic diode. Experimental results show that the energetic diode has typical rectification with a turn-on voltage of about 1.78 V and a reverse leakage current of about 3 × 10−4 A. When a constant voltage of 70 V loads to the energetic diode in the forward direction for about 0.14 s or 55 V loads in the reverse direction for about 0.17 s, the loaded power can excite the energetic diode exploding and the current rises to about 100 A. Due to the unique performance of the energetic diode, it has a double function of rectification and explosion. The energetic diode can be used as a logic element in the normal chip to complete the regular operation, and it can release energy to destroy the chip accurately.

Investigation of the leakage mechanism in multi-channel GaN-on-Si SBDs

This work presented the reverse leakage current (I R) mechanisms in multi-channel GaN-on-Si Schottky barrier diodes (SBDs). The device showed excellent performances in both ON and OFF-states thanks to the advanced multi-channel tri-gate architecture. The I R is dominated by thermal field emission at 25 °C–75 °C before pinch-off of the 2-dimensional electron gas (2DEG) channel in the Schottky region, due to the thinned Schottky barrier, which turned to be thermal emission (TE)-dominated under further elevated temperatures resulted from the small Schottky barrier height. Once the 2DEG channel is pinched off by the tri-anode, the I R is firstly dominated by Poole–Frenkel emission and then is trap-assisted tunneling after the full depletion of the channels beneath the field plates. These results are supported by excellent consistency between experimental results and theoretical models, offering a key understanding of multi-channel SBDs and shedding lights on this promising multi-channel technology for future energy conversion.