Passivation of InP with thin layers of MBE-grown CdS

Thin layers of CdS were grown on [100] n-InP by molecular beam epitaxy (MBE). Substrates were pre-treated in an ammonia/thiourea solution, then annealed at /spl sim/150-250/spl deg/C in vacuo prior to CdS growth. A single effusion cell with a polycrystalline CdS source was used. Reflection high energy electron diffraction (RHEED) analysis showed surface reconstruction following predeposition anneals at 200/spl deg/C of sulfur-passivated InP. Subsequent CdS deposition at 200/spl deg/C resulted in lattice-matched epitaxial layers in the metastable cubic phase, as observed with RHEED. X-ray photo-electron spectroscopy (XPS) analysis of the CdS/InP structures showed that the near-surface of InP is phosphorus deficient following the pre-deposition anneal, with an In/sub 2/S/sub 3/ layer present at the substrate/CdS interface. Subsequent processing of MIS structures with CdS layers (25-85 /spl Aring/) between the InP and SiO/sub 2/ resulted in MIS capacitors with consistently low density of interface states (2/spl times/10/sup 11/ eV/sup -1/ cm/sup -2/) and hysteresis (20 mV).