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While there have been many demonstrations on n-channel metal-oxide-semiconductor field-effect transistors (MOSFETs) in III-V semiconductors showing excellent electron mobility and high drive currents, hole mobility in III-V p-channel MOSFETs (pMOSFETs) has traditionally lagged in comparison to silicon. GaSb is an attractive candidate for high-performance III-V pMOSFETs due to its high bulk hole mobility. We fabricate and study GaSb pMOSFETs with an atomic layer deposition Al2O3 gate dielectric and a self-aligned source/drain formed by ion implantation. The band offsets of Al2O3 on GaSb were measured using synchrotron radiation photoemission spectroscopy. The use of a forming gas anneal to passivate the dangling bonds in the bulk of the dielectric was demonstrated. The density of interface states Dit was measured across the GaSb band gap using conductance measurements, and a midband-gap Dit of 3 × 1011/cm2 eV was achieved. This enabled pMOSFETs with a peak hole mobility value of 290 cm2/Vs.