Electrical characterization of CdS passivation on InP

InP surface passivation has been realized by a convenient chemical bath dep osition (CBD) of a thin CdS layer. For comparison, samples without any trea tments and/or with only a thin SiO2 layer were also prepared. Also studied was the effect of a thin layer of SiO2 deposited immediately after the CdS deposition. Schottky contacts were made on the CdS-passivated InP by electr on-beam deposition of Ti/Au. Electrical characterization was conducted by c urrent-voltage (I-V) and current-voltage-temperature (I-V-T) measurements. It was found that the electrical performance of the Schottky contacts of th e CdS-passivated InP samples was improved significantly. The thickness (dep osition time) of the CdS strongly affects the device electrical performance . The additional SiO2-on-CdS layer plays a key role in the process of InP s urface passivation. Post-treatment in the CdS deposition process also stron gly affects the surface morphology and electrical properties. Surface morph ology studied by atomic force microscopy (AFM) indicates that the surface r oughness increased after CdS deposition, though the degree of roughness is reverse proportional to the CdS process time. X-ray photoelectron spectrosc opy (XPS) shows that the CdS layer protects the InP substrate during the ox ide deposition.