Papers by Author: T. Khan

Abstract: GaN MOS capacitors were characterized to optimize the electric properties of SiO2/GaN interface. With optimized anneal conditions, an interface state density of 3.8×1010/cm2-eV was estimated at 0.19 eV near the conduction band and decreases deeper into the band gap. Enhancement-mode GaN MOSFETs were experimentally demonstrated on both p and n GaN epilayer with record high field-effect mobility of 167 cm2/V-s. Lateral RESURF-type GaN MOSFETs exhibit non-destructive high voltage (up to 940V) blocking capabilities. Other characterization including mobility orientation dependence, MOS-gated Hall mobility, current collapse and an NMOS inverter utilizing E/D mode GaN MOSFETs have also been experimentally demonstrated.

Abstract: The effect of incorporation of cesium with implantation on the electrical characteristics of SiO2/4H-SiC interface has been evaluated using MOS capacitors. With a cesium dosage of 1012 and 3x1012 cm-2 on deposited oxide re-oxidized in steam, effective oxide charge densities of - 1.4x1012 and -7.5x1011 cm-2 respectively were extracted and a cesium implant activation percentage of 33% was estimated from flatband voltage shift. Also, corresponding interfacial state densities of 2.5x1013 and 1.8x1013 cm-2-eV-1 near the conduction band edge were extracted from High-Low frequency C-V technique, showing a decreasing Dit with increasing Cs dosage.

Abstract: Both n-type and p-type GaN MOS capacitors with plasma-enhanced CVD-SiO2 as the gate oxide were characterized using both capacitance and conductance techniques. From a n type MOS capacitor, an interface state density of 3.8×1010/cm2-eV was estimated at 0.19eV near the conduction band and decreases deeper into the bandgap while from a p type MOS capacitor, an interface state density of 1.4×1011/cm2-eV 0.61eV above the valence band was estimated and decreases deeper into the bandgap. Unlike the symmetric interface state density distribution in Si, an asymmetric interface state density distribution with lower density near the conduction band and higher density near the valence band has been determined.