Advances in thin-film growth techniques have allowed the succesful fabrication of transistor devices, relying on heterostructure technology to enhance their electrical performance. Devices utilizing heterostructure epitaxy have demonstrated unity current-gain cut-off frequencies well in excess of 100 GHz and maximum oscillation frequencies beyond 200 GHz.
In this paper, the AlGaAs/InGaAs pseudomorphic HEMT is studied. X-ray Double-Crystal Diffractometry and Low-Temperature Photoluminescence Spectroscopy are used to demonstrate that the InGaAs pseudomorphic layer thickness of the strained layers, did not degrade the device switching speed. This suggests that HEMT devices with higher indium contents may be permitted without having to reduce the InGaAs layer thickness due to strain accommodation requirements. Since the increase in In content lowers the electron and hole effective masses and raises the low-field mobility, higher cut-off frequencies should be possible.