Simulation of Short-Channel Effects in N- and Ga-Polar AlGaN/GaN HEMTs

We have carried out 2-D simulation of N-polar and Ga-polar AlGaN/GaN HEMTs to investigate short-channel effects in highly scaled devices. N-polar HEMTs were found to have better drain-induced barrier lowering (DIBL) suppression than Ga-polar HEMTs. The short-channel effects were found to originate from the 2-D potential distribution in the channel and space-charge-limited current through the buffer. The inverted structure of the N-polar HEMT was found to provide better suppression of short-channel effects under idealized theoretical assumptions that were used in the model presented.

I. Introduction

AlGaN/GaN high electron mobility transistors (HEMTs) have shown considerable improvements in performance in the last two decades. The inherent material properties such as high breakdown field, high mobility and saturated velocity, high thermal conductivity, and wide band gap make AlGaN/GaN HEMTs a promising candidate for many microwave power and low-noise applications. The combination of improved growth structures and fabrication techniques have enabled devices to obtain an outstanding output power performance of 40 W/mm at 4 GHz [1], a unity current gain cutoff frequency of 160 GHz [2], and a maximum frequency of oscillation of 300 GHz [3].