Improvement of the GaSb/Al2O3 interface using a thin InAs surface layer

A major challenge in fabricating a high mobility (In)GaSb based transistor is reducing the density of trap states (D_it) at the III-V/high-k interface [1]. Unoccupied surface bonds react with ambient oxygen and create energy levels within the GaSb bandgap which limit Fermi level movement and degrade sub-threshold slope. InGaAs and other As-rich surfaces have been thoroughly investigated and exhibit significant trap state reduction with Ammonium Sulfide passivation and further native oxide reduction when exposed to TMA precursor used in ALD [2,3]. Interface engineering of GaSb is accomplished using an epitaxially grown 2nm InAs top layer. This GaSb/InAs gate stack has shown immense improvement in C-V characteristics and a significant reduction of D_it at the III-V/high-k interface.