Objective of this paper is to evaluate the performance of GaN HEMTs for high temperature applications. A sample
AlGaN/GaN HEMT structure is investigated using empirical data to evaluate the device performance at high
temperatures. Input transfer and output characteristics are the key focus along with transconductance and saturation
current. Intrinsic device parameters were calculated using measured S-parameter data at various frequencies under
different bias conditions and temperatures. Transconductance found at 398 °K is 2.5 mS for the entire gate width. DC
characteristics of the fabricated devices were examined at temperatures ranging from 295 °K to 363 °K. Maximum drain
current measured at room temperature was 214 mA which reduced to 192 mA at 363 °K. Reduction in saturation drain
current is found due to decrease in saturation carrier velocity and two dimensional electron density. Structure based
simulation tool ATLAS from Silvaco Int. is used for numerical simulations. The simulated device performance is in
good agreement with the empirical results. Experimental results for the critical parameters suggest that the device can
operate in the GHz Range for temperature up to 600 °K. Further enhancement of the model device is suggested upon
reviewing the measured results to improve the high-temperature performance.
In this paper an improved temperature model for AlGaN/GaN high electron mobility transistor (HEMT) is presented.
The two-dimensional Gaussian Standing Wave (GSW) equation is used to include the dependence of electron drift
velocity on the longitudinal electric field. The effects of channel conductance in the saturation region and the parasitic
resistance due to the undoped GaN buffer layer have been included. The effect of both spontaneous and piezoelectric
polarization induced charges at the AlGaN/GaN heterointerface has been incorporated. The proposed model is used to
determine the output current-voltage characteristics and small-signal microwave parameters of HEMTs. The major tasks
of this paper include the establishment of the compact model including the polarization effects and the validation of the
analytical results and experimental data with numerical simulator. High <i>f</i><sub>T</sub> (10-70 GHz) values and high current levels
(~650 mA/mm) are achieved. The calculated critical parameters and the simulation results suggest that the performance
of the proposed device degrades at elevated temperatures.