Electron transport properties in the Al0.15Ga0.85N/GaN heterostructure fiel
d 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 wit
h increasing the temperature, with the lower decrease ratio at higher tempe
ratures, and moreover, shown to be less dependent on the 2DEG density at hi
gher temperatures. These features well agree with those of the longitudinal
optical phonon-limited mobility theoretically predicted, although the effe
ct of alloy and interface scattering should further be examined and analyze
d. 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-do
ped 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 att
ractive as the channel material when higher-voltage and higher-temperature
device operation is required. (C) 2001 American Institute of Physics.