Temperature-dependent nonlinearities in GaN/AlGaN HEMTs

Abstract

Temperature-dependent nonlinearities of GaN/AlGaN HEMTs are reported. The large-signal device model of the transistor is obtained by using a physics-based analysis. The model parameters are obtained as functions of bias voltages and temperature. The analysis of the device has been carried out using a time-domain technique. f/sub max/ for a 0.23 /spl mu/m/spl times/100 /spl mu/m Al/sub 0.13/Ga/sub 0.87/N/GaN FET is calculated as 69 GHz at 300 K, while at 500 K, f/sub max/ decreases to 30 GHz, which are in agreement with the experimental data within 7% error. f/sub max/ as obtained from calculated unilateral gain, decreases monotonically with increasing temperature. For shorter gate lengths irrespective of the operating temperature f/sub max/ is less sensitive to bias voltage scaling. For longer gate length devices, f/sub max/ becomes less sensitive to the bias voltage scaling at elevated temperatures. 1-dB compression point (P/sub 1-dB/) at 4 GHz for a 1 /spl mu/m/spl times/500 /spl mu/m Al/sub 0.15/Ga/sub 0.85/N/GaN FET is 13 dBm at 300 K. At 500 K, P/sub 1-dB/ decreases to 2.5 dBm for the same operating frequency. Similar results for output referred third intercept point (OIP3) are reported for different gate length devices.