Abstract
Metamorphic high electron mobility transistor (M-HEMT) structures have been grown on GaAs substrates by molecular beam epitaxy (MBE). Linearly graded and the step-graded InGaAs and InAlAs buffer layers have been compared, and TEM, PL and low-temperature Hall have been used to analyze the properties of the buffer layers and the M-HEMT structure. For a single-delta-doped M-HEMT structure with an In 0.53Ga 0.47As channel layer and a 0.8 μm step-graded InAlAs buffer layer, room-temperature mobility of 9000 cm 2/V s and a sheet electron density as high as 3.6×10 12/cm 2 are obtained. These results are nearly equivalent to those obtained for the same structure grown on an InP substrate. A basic M-HEMT device with 1 μm gate was fabricated, and g m is larger than 400 mS/mm.
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