ANALYSIS OF THIN CDS LAYERS ON INP FOR IMPROVED METAL-INSULATOR-SEMICONDUCTOR DEVICES

Cadmium sulfide (CdS) layers were deposited from an aqueous solution o f thiourea, cadmium sulfate, and ammonia on (100) n-InP at 60-95 degre es C. X-ray photoelectron spectroscopy showed that the deposition proc ess effectively removes native oxides on InP and forms a protective la yer for subsequent dielectric deposition. Surface analysis also showed that the InP surface is not P deficient following oxide deposition on CdS-treated InP. Capacitance-voltage and conductance-voltage measurem ents of metal-insulator-semiconductor (MTS) capacitors were used to co mpare samples with and without CdS films between InP and a deposited i nsulator. Capacitance-voltage response of CdS-treated MIS structures s howed well-defined regions of accumulation, depletion, and inversion. The interface-state density at midgap was reduced from 5X10(11) to 6X1 0(10) eV(-1) cm(-2) with CdS treatment. Depletion-mode MIS field-effec t transistors made using this new passivation technique exhibited supe rior device performance to that of untreated samples.