Plasma deposited amorphous silicon passivation layers on InAs surfaces

The compound semiconductors (InAs, GaSb, AlSb) having nearly matched lattice constants (≈6.1 Å) 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 hydrogen-diluted 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.