Quantum-Well p-Channel AlGaAs/InGaAs/GaAs Heterostructure Insulated-Gate Field-Effect Transistors with Very High Transconductance

We describe quantum-well p-channel pseudomorphic Al-GaAs/InGaAs/GaAs heterostructure insulated-gate field-effect transistors (HIGFET's) with enhanced hole mobility. The room-temperature transconductance, transconductance parameter, and maximum drain current were as high as 113 mS/mm, 305 mS/V/mm, and 94 mA/mm, respectively, in 0.8-Μm gate devices. Transconductance, transconductance parameter, and maximum drain current as high as 175 mS/mm, 800 mS/V/mm, and 180 mA/mm, respectively, were obtained in 1-Μm p-channel devices at 77 K. From the device data we deduced hole field-effect mobilities of 860 cm2/V. s at 300 K and 2815 cm2/V. s at 77 K. The gate current causes the transconductance to drop (and even to change sign) at large voltage swings. Further improvement of the device characteristics may be obtained by minimizing the gate current. To this end we propose to use a new type of device structure that we call the dipole heterostructure insulated-gate field-effect transistor. The p-channel version of this device utilizes an n+ gate and either inverted p+ modulation doping or a p-doped channel. Complementary n-channel devices utilize a p+ gate and either inverted n+ modulation doping or an n-doped channel.