Chemical and electrical properties of (NH₄)₂S passivated GaSb surface

The surface chemical properties of gallium antimonide (GaSb) after ammonium sulfide ((NH₄)₂S) solution passivation have been studied by X-ray photoelectron spectroscopy (XPS), time of flight secondary ion mass spectroscopy (TOF-SIMS) and I–V measurement. An advantage of neutral (NH₄)₂S + S solution over pure (NH₄)₂S solution and alkaline (NH₄)₂S + S solution has been found in the ability to passivate the GaSb surface by contrast and comparison. It has been found that alkaline (NH₄)₂S + S solution passivation effectively removes oxides of the GaSb surface and forms sulfide products to improve device performance. TOF-SIMS complementally demonstrates that pure (NH₄)₂S passivation did form sulfide products, which are too soluble to really exist. The lowest roughness determined using a 3D optical profilometer and the highest improved SBD quality proved that neutral (NH₄)₂S + S solution passivation worked much better in improving the surface properties of GaSb. (paper)