Optimization of the $\hbox {Al}_{2}\hbox {O}_{3}/ \hbox {GaSb}$ Interface and a High-Mobility GaSb pMOSFET

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 D_it was measured across the GaSb band gap using conductance measurements, and a midband-gap D_it of 3 × 10¹¹/cm² eV was achieved. This enabled pMOSFETs with a peak hole mobility value of 290 cm²/Vs.