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The threshold voltage (Vth) of the p-channel metal–oxide–semiconductor field-effect transistors (MOSFETs) is investigated via Silvaco-Atlas simulations. The main factors which influence the threshold voltage of p-channel GaN MOSFETs are barrier height Φ1,p, polarization charge density σb, and equivalent unite capacitance Coc. It is found that the thinner thickness of p-GaN layer and oxide layer will acquire the more negative threshold voltage Vth, and threshold voltage |Vth| increases with the reduction in p-GaN doping concentration and the work-function of gate metal. Meanwhile, the increase in gate dielectric relative permittivity may cause the increase in threshold voltage |Vth|. Additionally, the parameter influencing output current most is the p-GaN doping concentration, and the maximum current density is 9.5 mA/mm with p-type doping concentration of 9.5 × 1016 cm−3 at VGS = –12 V and VDS = –10 V. [ABSTRACT FROM AUTHOR]

The key parameters of vertical AlN Schottky barrier diodes (SBDs) with variable drift layer thickness (DLT) and drift layer concentration (DLC) are investigated. The specific on-resistance (Ron,sp) decreased to 0.5 mΩ ⋅ cm2 and the breakdown voltage (VBR) decreased from 3.4 kV to 1.1 kV by changing the DLC from 1015 cm−3 to 3 × 1016 cm−3. The VBR increases from 1.5 kV to 3.4 kV and the Ron,sp also increases to 12.64 mΩ ⋅ cm2 by increasing DLT from 4-μm to 11-μm. The VBR enhancement results from the increase of depletion region extension. The Baliga's figure of merit (BFOM) of 3.8 GW/cm2 was obtained in the structure of 11-μm DLT and 1016 cm−3 DLC without FP. When DLT or DLC is variable, the consideration of the value of BFOM is essential. In this paper, we also present the vertical AlN SBD with a field plate (FP), which decreases the crowding of electric field in electrode edge. All the key parameters were optimized by simulating based on Silvaco-ATLAS. [ABSTRACT FROM AUTHOR]

In this paper, we carried out an analysis of the breakdown characterization method by the investigation on off-state leakage currents and breakdown curves. For conventional breakdown, seven kinds of breakdown curves are summarized and it is found that only two of them can be shown by the conventional three-terminal breakdown characterization method reasonably. For the other five kinds of breakdown curves, the value of the gate leakage current is larger than that of the drain leakage current for a certain drain-bias range. Besides, the source leakage current cannot represent the buffer leakage current, and the values and signs of them are different. These problems contradict the conventional characterization method, indicating that the conventional method should be modified to characterize the breakdown mechanisms correctly. The similar problems also exist for time-dependent breakdown. The buffer and drain-gate leakage currents were obtained by a simple method and the conventional breakdown characterization method was modified by using these two currents. The problems in the conventional breakdown characterization method are solved by using the modified method. Experiments indicate that the modified breakdown characterization method is crucial to investigate the breakdown mechanisms, especially when source-gate leakage current cannot be neglected compared with the buffer leakage current. [ABSTRACT FROM AUTHOR]

In this paper the trapping effects in Al2O3/In0.17Al0.83N/GaN MOS-HEMT (here, HEMT stands for high electron mobility transistor) are investigated by frequency-dependent capacitance and conductance analysis. The trap states are found at both the Al2O3/InAlN and InAlN/GaN interface. Trap states in InAlN/GaN heterostructure are determined to have mixed de-trapping mechanisms, emission, and tunneling. Part of the electrons captured in the trap states are likely to tunnel into the two-dimensional electron gas (2DEG) channel under serious band bending and stronger electric field peak caused by high Al content in the InAlN barrier, which explains the opposite voltage dependence of time constant and relation between the time constant and energy of the trap states. [ABSTRACT FROM AUTHOR]

Frequency-dependent conductance measurements were carried out to investigate the trap states induced by reactive ion etching in AlGaN/GaN high-electron-mobility transistors (HEMTs) quantitatively. For the non-recessed HEMT, the trap state density decreases from 2.48 × 1013 cm−2·eV−1 at an energy of 0.29 eV to 2.79 × 1012 cm−2·eV−1 at ET = 0.33 eV. In contrast, the trap state density of 2.38 × 1013–1.10 × 1014 cm−2·eV−1 is located at ET in a range of 0.30–0.33 eV for the recessed HEMT. Thus, lots of trap states with shallow energy levels are induced by the gate recess etching. The induced shallow trap states can be changed into deep trap states by 350 °C annealing process. As a result, there are two different types of trap sates, fast and slow, in the annealed HEMT. The parameters of the annealed HEMT are ET = 0.29–0.31 eV and DT = 8.16 × 1012–5.58 × 1013 cm−2·eV−1 for the fast trap states, and ET = 0.37–0.45 eV and DT = 1.84 × 1013 − 8.50 × 1013 cm−2·eV−1 for the slow trap states. The gate leakage currents are changed by the etching and following annealing process, and this change can be explained by the analysis of the trap states. [ABSTRACT FROM AUTHOR]

We report Al0.30Ga0.70N/GaN/Al0.07Ga0.93N double heterostructure high electron mobility transistors with a record saturation drain current of 1050 mA/mm. By optimizing the graded buffer layer and the GaN channel thickness, both the crystal quality and the device performance are improved significantly, including electron mobility promoted from 1535 to 1602 cm2/V·s, sheet carrier density improved from 0.87×1013 to 1.15×1013 cm−2, edge dislocation density reduced from 2.4×109 to 1.3×109 cm−2, saturation drain current promoted from 757 to record 1050 mA/mm, mesa leakage reduced by two orders in magnitude, and breakdown voltage promoted from 72 to 108 V. [ABSTRACT FROM AUTHOR]

The influence of an N2O plasma pre-treatment technique on characteristics of AlGaN/GaN high electron mobility transistor (HEMT) prepared by using a plasma-enhanced chemical vapor deposition (PECVD) system is presented. After the plasma treatment, the peak transconductance (gm) increases from 209 mS/mm to 293 mS/mm. Moreover, it is observed that the reverse gate leakage current is lowered by one order of magnitude and the drain current dispersion is improved in the plasma-treated device. From the analysis of frequency-dependent conductance, it can be seen that the trap state density (DT) and time constant (τT) of the N2O-treated device are smaller than those of a non-treated device. The results indicate that the N2O plasma pre-pretreatment before the gate metal deposition could be a promising approach to enhancing the performance of the device. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]