2D hole transport in GaAs MOSFETs

We have fabricated enhancement-mode p-channel GaAs MOSFETs on the (100) surface of undoped GaAs/Al$_{x}$Ga$_{1-x}$As heterostructures, using atomic-layer-deposited Al$_{2}$O$_{3 }$dielectric and Ti/Au gate, and measured their transport properties. The capacitively induced 2D hole density (p), determined from Shubnikov-de Haas oscillations, can be tuned from 9x10$^{9 }$to 3x10$^{11}$cm$^{-2 }$by applying a negative gate bias. Within this range, the effective capacitance is close to that of an ideal parallel plate capacitor, and the leakage current remains virtually zero. The highest possible density is limited by the heterostructure design, not by gate leakage. The 2D hole mobility at T=0.3K increases with p and saturates at 6.3x10$^{5}$ cm$^{2}$/Vs for p$>$2.3x10$^{11}$cm$^{-2}$. In this talk, we present data on transistor drain current-voltage characteristics, as well as magneto transport and the quantum Hall effects.