High-temperature electron transport properties in AlGaN/GaN heterostructures

Abstract
Electron transport properties in the Al 0.15 Ga 0.85 N/GaN heterostructurefield effect transistors(HFETs) have been examined from room temperature up to 400 ° C . The temperature dependencies of the two-dimensional electron gas(2DEG)mobility have been systematically measured for the samples with different 2DEG densities. The 2DEGmobility has been shown to decrease with increasing the temperature, with the lower decrease ratio at higher temperatures, and moreover, shown to be less dependent on the 2DEG density at higher temperatures. These features well agree with those of the longitudinal optical phonon-limited mobilitytheoretically predicted, although the effect of alloy and interface scattering should further be examined and analyzed. The observed 2DEGmobilities at 400 ° C were as high as from 100 to 120 cm 2 /V s , directly providing the evidence for suitability of the HFET of this material system for high-temperature applications. Moreover, Si-doped Al 0.15 Ga 0.85 N single layer has been shown to exhibit a relatively high bulk mobility of 50 cm 2 /V s at 400 ° C , suggesting that AlGaN is attractive as the channel material when higher-voltage and higher-temperature device operation is required.