Improved surface and electrical properties of passivated GaSb with less alkaline sulfide solution

The surface quality of HCl-etched and ammonium sulfide [(NH4)2S]-based treated bulk n-GaSb(100) were compared using x-ray photoelectron spectroscopy (XPS) and TOF-SIMS. It has been found that native oxides present on the GaSb surface are more effectively removed when etched with concentrated HCl solution. With additional [(NH4)2SO4+S] substances or hydrogen ions in the passivation solution, the treated samples displayed significant reduction of native oxides and formation of the sulfides compared with pure (NH4)2S solution. The treated samples also result in a noteworthy improvement in the current-voltage (I-V) characteristics of Au/n-GaSb Schottky contacts, as evidenced by the lower ideality factor (n), higher barrier height (Φb) and higher rectification ratio at ±0.2 V. The I-V measurement provided definitive confirmation of XPS and TOF-SIMS results, establishing the need for less alkaline solution for greater passivation stability.