Plasma deposited amorphous silicon passivation layers on InAs surfaces

The compound semiconductors (InAs, GaSb, AlSb) having nearly matched lattice constants (approximate to 6.1 angstrom) are of great interest in fabrication of infrared micro/optoelectronics, but are hampered significantly by a high density of interface states that lead to degenerately doped surface layers. Native oxides are a cause of interface states, as well as a barrier to the effective passivation of dangling bonds, and must be removed. Re-oxidation must then be prevented prior to deposition of a passivant. We demonstrate effective removal of the native oxide of InAs through utilization of an amorphous silicon plasma enhanced chemical vapor deposition process. A hydrogendiluted silane plasma provides a reducing environment to react and remove indium and arsenic oxide species while a thin layer of amorphous silicon is grown to passivate and prevent re-oxidation of the InAs surface. The reduction of native oxide species via hydrogen-diluted argon plasma as a pretreatment prior to amorphous silicon was also explored. The surface chemistry is verified via depth profiling X-ray photoelectron spectroscopy, and the impact of a hydrogen-argon plasma pretreatment investigated to further reduce oxygen concentration at the InAs/amorphous silicon interface.