Electrical and physical characterization of the Al₂O₃/ p -GaSb interface for 1%, 5%, 10%, and 22% (NH₄)₂S surface treatments

In this work, the impact of ammonium sulfide ((NH₄)₂S) surface treatment on the electrical passivation of the Al₂O₃/p-GaSb interface is studied for varying sulfide concentrations. Prior to atomic layer deposition of Al₂O₃, GaSb surfaces were treated in 1%, 5%, 10%, and 22% (NH₄)₂S solutions for 10min at 295K. The smallest stretch-out and flatband voltage shifts coupled with the largest capacitance swing, as indicated by capacitance-voltage (CV) measurements, were obtained for the 1% treatment. The resulting interface defect trap density (D_it) distribution showed a minimum value of 4×10¹²cm^-2eV^-1 at E_v+0.27eV. Transmission electron microscopy and atomic force microscopy examination revealed the formation of interfacial layers and increased roughness at the Al₂O₃/p-GaSb interface of samples treated with 10% and 22% (NH₄)₂S. In combination, these effects degrade the interface quality as reflected in the CV characteristics.