Sanaz K. Gardner

Experimental observation and physics of “negative” capacitance and steeper than 40mV/decade subthreshold swing in Al 0.83 In 0.17 N/AlN/GaN MOS-HEMT on SiC substrate

GaN is a promising material for LED lighting [1], high voltage power electronics [2] and high power RF applications [3]. GaN HEMT and MOS-HEMT with AlGaN [4] or AlInN [5] polarization layer have been widely studied. In this work we investigate the effects of Al_0.83In_0.17N polarization layer thickness scaling on the device characteristics of Al_0.83In_0.17N/AlN/GaN MOS-HEMTs on SiC substrates. We have experimentally observed “negative” capacitance and subthreshold swing (SS) steeper than 40 mV/dec in GaN MOS-HEMTs with thin Al_0.83In_0.17N polarization layer, where composition modulation of Al% and In% is observed.

High-performance low-leakage enhancement-mode high-K dielectric GaN MOSHEMTs for energy-efficient, compact voltage regulators and RF power amplifiers for low-power mobile SoCs

We have fabricated L_G=90nm high-K dielectric enhancement-mode (e-mode) GaN MOS-HEMT which shows low I_OFF=70nA/μm (V_D=3.5V, V_G=0V), low R_ON=490Ω-μm, high I_D,max=1.4mA/μm, and excellent power-added efficiency (PAE) of 80% at RF output power density (RF Pout) of 0.55W/mm (V_D=3.5V, f=2.0GHz). These results represent (i) >3.6X lower RON at equivalent breakdown voltage (BV_D) than industry-standard Si voltage regulator (VR) transistors, and (ii) >10% better PAE at matched RF Pout or >50% higher RF Pout at matched PAE than industry-standard GaAs RF power amplifier (PA) transistors, all at mobile SoC-compatible voltages. These results make GaN MOS-HEMTs attractive for realizing energy-efficient, compact voltage regulators and RF power amplifiers for mobile SoC. This work shows, for the first time, that the application space of GaN electronics can be expanded beyond the existing high-voltage power and RF electronics (e.g. automobile, power conversion, base-station, radar) to include low-power mobile SoCs.