High-temperature electron transport properties in AlGaN/GaN heterostructures

Electron transport properties in the Al0.15Ga0.85N/GaN heterostructure field effect transistors (HFETs) have been examined from room temperature up to 400 degreesC. The temperature dependencies of the two-dimensional electron gas (2DEG) mobility have been systematically measured for the samples with different 2DEG densities. The 2DEG mobility 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 mobility theoretically predicted, although the effect of alloy and interface scattering should further be examined and analyzed. The observed 2DEG mobilities at 400 degreesC 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 Al0.15Ga0.85N single layer has been shown to exhibit a relatively high bulk mobility of 50 cm(2)/V s at 400 degreesC, suggesting that AlGaN is attractive as the channel material when higher-voltage and higher-temperature device operation is required. (C) 2001 American Institute of Physics.