Forward Blocking Voltage Research Articles

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.

The Advantages and Applications of IGBT Compared with Conventional BJT and MOSFET

Nowadays, the power semiconductor devices have been used in many fields like wind power generation systems, the rail transit. Bipolar junction transistors (BJTs) and metal-oxide-semiconductor field-effect transistors (MOSFETs) as well as some other devices are the dominating the market. The insulated gate bipolar transistor (IGBT) as a mixed device of the BJT and the MOSFET, has a preeminent performance. In this paper, the characteristics of the punch through IGBT (PT-IGBT), the MOSFET and the BJT will be investigated by TCAD. Then the PT-IGBT is compared with the BJT and the MOSFET, for concluding its advantages. According to the simulation result, the PT-IGBT has the on-state current of 9*10-4A and the forward blocking voltage of 1200V, which are much higher than the other two devices. In the end of the paper, the development of the semiconductor devices is predicted, about the research trends.

A novel SiC power MOSFET with integrated polySi/SiC heterojunction freewheeling diode

The adoption of intrinsic body diode of SiC MOSFETs as freewheeling diode (FWD) always induces high conduction loss and reverse recovery loss, therefore it is highly desirable to integrate a low loss FWD in SiC MOSFET. In this paper, we propose a new concept of monolithically integrating a polySi/SiC heterojunction diode (HJD) in SiC planar MOSFET (HJDMOS) without sacrificing MOSFET cell density or increasing much processing complexity. The HJD is formed between the gate polysilicon and the SiC JFET region using the same polysilicon deposition, thus the MOSFET and FWD can share the JFET and drift region in a time-multiplexing way. The SiC HJDMOS not only inactivates the body diode by offering lower turn-on voltage but also shows excellent reverse recovery characteristics because the HJD behaves like a Schottky barrier diode. Meanwhile, the gate-to-drain charge (Q gd) and gate-to-drain capacitance (C gd) of the SiC HJDMOS are significantly reduced by 8.0 times and 4.6 times in comparison with the conventional MOSFET due to the reduction of the overlapping area of gate and drain region. With optimal selection of design parameters, the integrated device maintains good MOSFET performances with forward blocking voltage of >1200 V and specific on-resistance (R on,sp) of 2.2 mΩ cm2. Therefore, the obtained figure-of-merits ( and ) of SiC HJDMOS are improved by around 7.5 times and 4.3 times, respectively. The enhanced performances suggest that SiC HJDMOS is an excellent choice for high efficiency and high frequency power electronic applications.

Quasi-vertical GaN-on-Si reverse blocking power MOSFETs

We demonstrate quasi-vertical reverse blocking (RB) MOSFETs on 6.7 μm thick GaN grown on a 6 inch Si substrate by metalorganic chemical vapor deposition. The RB capability was achieved by replacing the ohmic drain with a quasi-vertical Schottky drain, resulting in a RB voltage of ∼300 V while preserving the ON-resistance (R on,sp). Schottky contacts on etched i-GaN surface were realized through an optimized fabrication process based on tetramethylammonium hydroxide treatments. The fabricated RB-MOSFET had a low R on,sp of 4.75 mΩ cm2, current density of ∼0.9 kA cm−2 and a forward blocking voltage of 570 V.

Design and Characterization of N-MCT with Low Vth Off-FET for High Current-drive Capability

In this paper, an N-MCT with a low threshold voltage of off-FET has been investigated by simulation and experiment. We have demonstrated the MCT with self-aligned spacer formation and recess process, which results in uniform off-FET channel length. And boron is implanted to adjust the threshold voltage of off-FETs. The threshold voltage of non-doped and proposed MCT was -1.2 V and 0.6 V, respectively. The forward blocking voltage of both MCTs was similar to 1800 V and the turn-on voltage of MCTs was 0.2 V and 0.75 V, respectively. The non-doped and proposed MCTs exhibit the same di/dt around 35.7 kA/㎲ and peak current of 2.69 kA. That is pointed out that this proposed MCT structure is promising because the current driving capability is improved without degradation of on-state characteristics.

1.3 kV Reverse-Blocking AlGaN/GaN MISHEMT With Ultralow Turn-On Voltage 0.25 V

A reverse-blocking AlGaN/GaN metal-insulator-semiconductor high electron mobility transistor (RB-MISHEMT) is proposed and fabricated. Compared with the conventional MISHEMT with ohmic drain, the proposed device features a hybrid Schottky-ohmic drain with a low work function Tungsten (W), based on which the state-of-the-art ultralow turn-on voltage ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${V} _{\mathrm{ on}}$ </tex-math></inline-formula> ) of 0.25 V could be realized without degradation in on-state characteristics. In addition, the fabricated RB-MISHEMT exhibits the excellent reverse blocking voltage of −1332 V (at <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${V} _{\mathrm{ GS}}= 0$ </tex-math></inline-formula> V) and forward blocking voltage of 1315 V (at <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${V} _{\mathrm{ GS}} = -15$ </tex-math></inline-formula> V) with a specific on-resistance ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${R} _{\mathrm{ on,sp}}$ </tex-math></inline-formula> ) of 3.5 <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 $ </tex-math></inline-formula> cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> , leading in the highest power figure-of-merit (FOM) of > 494 MW/cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> . The good thermal stability could also be observed in fabricated RB-MISHEMT. The corresponding operation mechanism of RB-MISHEMT are also revealed by Silvaco ATLAS simulations. These results demonstrate the great potential in power electronics applications.

Experimental Study on Displacement Damage Effects of Anode-Short MOS-Controlled Thyristor

The metal-oxide-silicon (MOS)-controlled thyristor (MCT) has been characterized by MOS-gating, high-current-rise rate, and high blocking capabilities. The anode-short MCT (AS-MCT) is distinguished from conventional MCT by an anode-short structure, which forms an extracting path for electron current at the gate ground and develops a normally-off characteristic. As a composite structure made of MOS and bipolar junction transistors, AS-MCT is susceptible to displacement damage (DD). For the first time, this article reports the DD effects on AS-MCT with the fast neutron flux in the range of 3.1 × 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">9</sup> - 5.5 × 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">13</sup> cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-2</sup> . Both the transfer and forward conductive characteristics are degraded subsequent to neutron exposures. When the neutron flux surpasses a critical value, the function failure of AS-MCT occurs, i.e., the AS-MCT cannot be latched up and enter into the thyristor-like conductivity mode, and, instead, remains in the insulated gate bipolar transistor-like conductivity mode. For the forward blocking characteristics (open gate), both the anode leakage current and forward blocking voltage increase subsequent to neutron exposures. To note, a novel phenomenon is observed for AS-MCT following neutron exposures, i.e., the forward current-voltage curve exhibiting “double snap-back effect.” This article proposes, from a device physics perspective, the mechanism behind the characteristics of degradation from DD in AS-MCT. The dependencies of the key parameters on neutron flux and the failure neutron flux are analytically modeled. Our models provide an excellent fit to the experimental data of the XND1 AS-MCT subjected to fission neutrons.

Improved Device Performance in AlGaN/GaN HEMT by Forming Ohmic Contact With Laser Annealing

An AlGaN/GaN high-electron-mobility transistor with a novel ohmic contact formation process based on conventional pulsed laser annealing is proposed. Compared with the conventional rapid thermal annealing process, the laser annealing (LA) process not only improves the surface morphology of ohmic contact metal but also exhibits a higher OFF-state breakdown voltage. An excellent rms roughness of 16.5 nm is observed by atomic force microscope which is 16.3% of the reference one. In a device with a gate-to-drain distance of 5 $\mu \text{m}$ , a forward blocking voltage of 442 V is obtained at ${V}_{\textsf {GS}} = -\textsf {8}$ V which has a 37.3% improvement compared with the conventional device. The device with LA process has lower contact resistance at actual working temperature (above 125 °C). The current transport mechanism is dominated by thermionic field emission through the ohmic contact. Moreover, the degradation of dynamic ON-resistance is significantly suppressed due to lower surface states by protecting the bare AlGaN layer from directly exposing under high temperature ambient.

Investigation of Porous Silicon-Based Edge Termination for Planar-Type TRIAC

This paper aims to investigate a porous silicon (PS)-based edge termination for planar type ac switch. TRIAC device prototypes, specifically dedicated to evaluate blocking performances, are fabricated by integrating electrochemical etching in device processing. A mixed porous morphology containing micro-, meso-, and macropores is obtained in a p-Type through-wafer-diffused via after anodization. The fabricated prototypes show PS-dependent blocking capabilities. The possible impacts of the anodization conditions and the physical features of PS on the electrical characteristics are discussed in detail. Low leakage currents ( $ ) have been demonstrated up to several hundred voltages for both bias polarities. The forward blocking voltage decreases with increasing PS thickness, while an opposite trend is observed for the reverse blocking voltage. This paper confirms the interest of PS as a potential insulating material for power device manufacture.

Positive-bevel edge termination for SiC reversely switched dynistor

The termination structure for the pulsed power switch SiC RSD (reversely switched dynistor) is studied in this paper. According to the structure characteristics of SiC RSD, the positive-bevel edge termination is designed. By establishing the two-dimensional numerical model, the function that the positive-bevel can reduce the surface electric field is proved. Combined the surface electric field and the area loss, 45° positive angle is selected. According to the process characteristics of SiC material, bevel dicing together with ICP (inductively coupled plasma) etching treatment is chosen to fabricate the positive-bevel edge termination in experiment. The forward blocking voltage of about 600V is acquired for the device. The optimal value for the etching depth is also discussed.

Mechanism of improving forward and reverse blocking voltages in AlGaN/GaN HEMTs by using Schottky drain

In this paper, we demonstrate that a Schottky drain can improve the forward and reverse blocking voltages (BVs) simultaneously in AlGaN/GaN high-electron mobility transistors (HEMTs). The mechanism of improving the two BVs is investigated by analysing the leakage current components and by software simulation. The forward BV increases from 72 V to 149 V due to the good Schottky contact morphology. During the reverse bias, the buffer leakage in the Ohmicdrain HEMT increases significantly with the increase of the negative drain bias. For the Schottky-drain HEMT, the buffer leakage is suppressed effectively by the formation of the depletion region at the drain terminal. As a result, the reverse BV is enhanced from −5 V to −49 V by using a Schottky drain. Experiments and the simulation indicate that a Schottky drain is desirable for power electronic applications.

Reverse blocking enhancement of drain field plate in Schottky-drain AlGaN/GaN high-electron mobility transistors

In this paper, we present the combination of drain field plate (FP) and Schottky drain to improve the reverse blocking capability, and investigate the reverse blocking enhancement of drain FP in Schottky-drain AlGaN/GaN high-electron mobility transistors (HEMTs). Drain FP and gate FP were employed in a two-dimensional simulation to improve the reverse blocking voltage (VRB) and the forward blocking voltage (VFB). The drain-FP length, the gate-FP length and the passivation layer thickness were optimized. VRB and VFB were improved from −67 V and 134 V to −653 V and 868 V respectively after optimization. Simulation results suggest that the combination of drain FP and Schottky drain can enhance the reverse blocking capability significantly.

Design and Experimental Study of 4H-SiC Trenched Junction Barrier Schottky Diodes

This paper presents the design, fabrication, and experimental analysis of 1200 V 4H-SiC trenched junction barrier Schottky (TJBS) diodes. Design considerations and device performances of the TJBS devices are compared with those of the conventional planar JBS diodes via numerical simulation, analytical modeling, and experiments. It was found that, for conventional planar JBS diodes, due to its limited P <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">+</sup> implantation depth, there is a tight tradeoff between forward ON-resistance and blocking voltage. This does not only put stringent requirement on obtaining a narrow photolithography line width ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="TeX">\(\sim 1.5\) </tex-math></inline-formula> <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="TeX">\(\mu \) </tex-math></inline-formula> m), but also makes the device design window narrow. The TJBS diodes can substantially alleviate such tradeoff and obtain a larger design window that enables good reverse blocking and forward conduction capabilities at the same time. As a result, this structure demands less restriction on line width control (2.2–3.2 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="TeX">\(\mu \) </tex-math></inline-formula> m) of the fabrication process and hence can improve the device yield.

Trapezoid mesa와 Half Sidewall Technique을 이용한 4H-SiC Trench MOS Barrier Schottky(TMBS) Rectifier

In this study, an 4H-SiC Trench MOS Barrier Schottky (TMBS) rectifier which utilizes the trapezoid mesa structure and the upper half of the trench sidewall is proposed to improve the forward voltage drop and reverse blocking voltage concurrently. The proposed 4H-SiC TMBS rectifier reduces the forward voltage drop by 12% compared to the conventional 4H-SiC TMBS rectifier with the tilted sidewall and improves the reverse blocking voltage by 11% with adjusting the length of the upper sidewall. The Silvaco T-CAD was used to analyze the electrical characteristics.

Influence of a drain field plate on the forward blocking characteristics of an AlGaN/GaN high electron mobility transistor

In this paper, the influence of a drain field plate (FP) on the forward blocking characteristics of an AlGaN/GaN high electron mobility transistor (HEMT) is investigated. The HEMT with only a gate FP is optimized, and breakdown voltage VBR is saturated at 1085 V for gate—drain spacing LGD ≥ 8 μm. On the basis of the HEMT with a gate FP, a drain FP is added with LGD = 10 μm. For the length of the drain FP LDF ≤ 2 μm, VBR is almost kept at 1085 V, showing no degradation. When LDF exceeds 2 μm, VBR decreases obviously as LDF increases. Moreover, the larger the LDF, the larger the decrease of VBR. It is concluded that the distance between the gate edge and the drain FP edge should be larger than a certain value to prevent the drain FP from affecting the forward blocking voltage and the value should be equal to the LGD at which VBR begins to saturate in the first structure. The electric field and potential distribution are simulated and analyzed to account for the decrease of VBR.

An AlGaN/GaN HEMT with enhanced breakdown and a near-zero breakdown voltage temperature coefficient

An AlGaN/GaN high-electron mobility transistor (HEMT) with a novel source-connected air-bridge field plate (AFP) is experimentally verified. The device features a metal field plate that jumps from the source over the gate region and lands between the gate and drain. When compared to a similar size HEMT device with a conventional field plate (CFP) structure, the AFP not only minimizes the parasitic gate to source capacitance, but also exhibits higher OFF-state breakdown voltage and one order of magnitude lower drain leakage current. In a device with a gate to drain distance of 6 μm and a gate length of 0.8 μm, three times higher forward blocking voltage of 375 V was obtained at VGS = −5 V. In contrast, a similar sized HEMT with a CFP can only achieve a breakdown voltage no higher than 125 V using this process, regardless of device dimensions. Moreover, a temperature coefficient of 0 V/K for the breakdown voltage is observed. However, devices without a field plate (no FP) and with an optimized conventional field plate (CFP) exhibit breakdown voltage temperature coefficients of −0.113 V/K and −0.065 V/K, respectively.

Fabrication of a P-Channel SiC-IGBT with High Channel Mobility

We fabricated and characterized an ultrahigh voltage (&gt;10kV) p-channel silicon carbide insulated gate bipolar transistor (SiC-IGBT) with high channel mobility. Higher field-effect channel mobility of 13.5 cm2/Vs was achieved by the combination of adopting an n-type base layer with a retrograde doping profile and additional wet re-oxidation annealing (wet-ROA) at 1100°C in the gate oxidation process. The on-state characteristics of the p-channel SiC-IGBT at 200°C showed the low differential specific on-resistance of 24 mΩcm2 at VG = -20 V. The forward blocking voltage of the p-channel SiC-IGBT at 25°C was 10.2 kV a the leakage current density of 1.0 μA/cm2.

Breakdown-Voltage-Enhancement Technique for RF-Based AlGaN/GaN HEMTs With a Source-Connected Air-Bridge Field Plate

An AlGaN/GaN high-electron-mobility transistor (HEMT) with a novel source-connected air-bridge field plate (AFP) is proposed. The device features a metal field plate (FP) that jumps from the source over the gate region and lands between the gate and drain. The fabrication process is based on a commercially available radio-frequency GaN-on-SiC technology. Device characteristics for this work were optimized via layout changes only. When compared to a similar-sized HEMT device with a conventional FP structure, the AFP not only minimizes the parasitic gate-to-source capacitance but also exhibits a higher off-state breakdown voltage and one order of magnitude lower drain leakage current. In a device with a gate-to-drain distance of 6 μm and a gate length of 0.8 μm, a three-times-higher forward blocking voltage of 375 V was obtained at VGS = -5 V. In contrast, a similar-sized HEMT with a conventional FP can only achieve a breakdown voltage no higher than 125 V using this process, regardless of device dimensions. The specific on-resistance for the device with the proposed AFP is 0.58 mΩ·cm2 at VGS = 0 V, which compares favorably with 0.79 mΩ·cm2 for the best device with a conventional FP.

Design and optimization of linearly graded-doping junction termination extension for 3.3-kV-class IGBTs

A linearly graded-doping junction termination extension (LG-JTE) for 3.3-kV-class insulated gate bipolar transistors (IGBTs) was proposed and experimentally investigated. Unlike conventional multi-implantation utilizing more than one photolithography step, a single mask with injection window widths varied linearly away from the main junction to the edge was implemented in this proposed structure. Based on the simulation results, IGBTs with LG-JTE structures were successfully fabricated on the domestic process platform. The fabricated devices exhibited a 3.7 kV forward-blocking voltage, which is close to the theoretical value of an ideal parallel plane case. This is the first success in fabrication 3.3-kV-class IGBT in a domestic application.

Schottky-Ohmic Drain AlGaN/GaN Normally Off HEMT With Reverse Drain Blocking Capability

In this letter, we propose an AlGaN/GaN normally off high-electron mobility transistor (HEMT) with reverse drain blocking capability. The device features a Schottky-ohmic drain electrode in which a Schottky-controlled normally off channel is inserted between the gate and the conventional ohmic drain contact. Under negative reverse drain bias, the normally off channel provides an energy barrier that effectively blocks the reverse current conduction while contributing only 0.55 V onset voltage in the forward-biased on state. In a device with a gate-drain distance of 9 m, a reverse blocking voltage of -321 V was obtained at V <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">GS</sub> = 0 V, comparable with the forward blocking voltage of 351 V; at V <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">GS</sub> = 3 V, the reverse blocking voltage was -276 V. The new HEMT also exhibits no degradation in drain saturation current and does not need extra photomask or process steps to fabricate. When forward biased at V <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">GS</sub> = 3 V , the proposed device achieved a specific on resistance of 1.97 mΩ · m <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> .