GaSb Inversion-Mode PMOSFETs With Atomic-Layer-Deposited $\hbox {Al}_{2}\hbox {O}_{3}$ as Gate Dielectric

GaSb inversion-mode PMOSFETs with atomic-layer-deposited (ALD) Al₂O₃ as gate dielectric are demonstrated. A 0.75- μm-gate-length device has a maximum drain current of 70 mA/mm, a transconductance of 26 mS/mm, and a hole inversion mobility of 200 cm²/V ·s. The off-state performance is improved by reducing the ALD growth temperature from 300°C to 200°C. The measured interface trap distribution shows a low interface trap density of 2 × 10¹²/cm²·eV near the valence band edge. However, it increases to 1 - 4 ×10¹³/cm² ·eV near the conduction band edge, leading to a drain current on-off ratio of 265 and a subthreshold swing of ~ 600 mV/decade. GaSb, similar to Ge, is a promising channel material for PMOSFETs due to its high bulk hole mobility, high density of states at the valence band edge, and, most importantly, its unique interface trap distribution and trap neutral level alignment.