Characterization of sulfur passivated n-GaSb using transmission electron microscopy and the influence of passivation on ohmic contact resistance

Transmission electron microscopy has been used to study sulfur passivation of (100) n-GaSb. An amorphous Ga-S layer forms during passivation, with a thickness dependent on the duration of passivation. Minimal oxygen is present in the sulfide layer. The sulfide layer remains amorphous when annealed at 350 °C for 10 min. After 20 min at 500 °C, the layer becomes nanocrystalline and is enriched with Ga from the GaSb, with voids and Sb precipitates forming at the sulfide/GaSb interface. If used as a premetallization surface preparation, sulfur passivation can inhibit reaction between a contact metallization and GaSb; however, with an appropriate choice of passivation conditions to minimize the thickness of the sulfide layer, it can instead promote a more uniform reaction between the metal and semiconductor than is achieved with a conventional surface preparation. It can also lead to a reduced ohmic contact resistance.