Transport properties of the two-dimensional hole gas in p-type heterostructure field-effect transistors

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Abstract
A fabrication process is presented for p‐type AlGaAs/GaAs heterostructure field‐effect transistors to be applied between 15 and 300 K. Different gate metallizations were tested. The resulting barrier heights varied between 0.4 and 0.85 eV. Two different samples were investigated. Sample I contained a thick spacer to achieve maximum mobility (μHall,15 K =27 000 cm2 /V s, ns,l5 K =4.5×1011 cm−2 ) and showed transconductances of 3, 15, and 25 mS/mm at 300, 77, and 15 K, respectively. Sample II was grown with a thinner spacer to increase the sheet carrier concentration (μHall,15 K =16 000 cm2 /V s, ns,15 K =9.2×1011 cm−2) and showed transconductances of 15, 35, and 45 mS/mm at 300, 77, and 15 K, respectively. The magnetotransconductance method was applied to investigate the transport properties of the two‐dimensional hole gas within the devices. The field dependence of the mobility was measured and the drift velocity of the holes was deduced from the experimental data.