Electrical Characterization of CdS Passivation on InP

Abstract

InP surface passivation has been realized by a convenient chemical bath deposition (CBD) of a thin CdS layer. For comparison, samples without any treatments 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 electron-beam deposition of Ti/Au. Electrical characterization was conducted by current-voltage (I-V) and current-voltage-temperature (I-V-T) measurements. It was found that the electrical performance of the Schottky contacts of the CdS-passivated InP samples was improved significantly. The thickness (deposition 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 surface passivation. Post-treatment in the CdS deposition process also strongly affects the surface morphology and electrical properties. Surface morphology studied by atomic force microscopy (AFM) indicates that the surface roughness increased after CdS deposition, though the degree of roughness is reverse proportional to the CdS process time. X-ray photoelectron spectroscopy (XPS) shows that the CdS layer protects the InP substrate during the oxide deposition.

Cadmium sulfide passivation of InGaAs/InP mesa p-i-n photodiodes

“…The inclusion of this final chemical treatment and anneal was found to produce more uniform electrical results in this and other works. [10][11][12][13][14] A similar recipe to the one presented here produced dramatic reductions in interface state trap density on InP based MIS structures as measured by high and low frequency CV techniques. [10][11][12][13] Sample D was prepared in an identical fashion to sample C with the addition of a 2000 Å SiO 2 capping layer deposited by lowtemperature CVD.…”

“…Another promising technique, sulfur passivation using chemical baths, was shown to be particularly effective in reducing surface states in III-V compounds in a variety of device types. [10][11][12][13][14] Although the use of (NH 4 ) 2 S and (NH 4 ) 2 S x chemical baths are cited most frequently in the literature, chemically deposited cadmium sulfide (CdS) has also been shown to improve device performance through the reduction of interface states in InP MIS diodes, 10 MIS capacitors, [11][12][13][14] MSM devices, 10 MISFETs, 13 Schottky contacts, 14 and HEMTs. 10 In this report, we present the results of applying the chemical bath deposition (CBD) CdS process of Ref.…”

Characterization of the passivation of CdS thin films grown by chemical bath deposition on InP

“…The deposition of CdS by chemical bath deposition (CBD) is one of the methods most used to improve and stabilize the InP surface. The passivating properties of thin CdS layers on InP have been reported, showing that the chemical bath treatment removes native oxides of InP and forms a stable layer of CdS [3,4]. Furthermore, there is an excellent lattice match between zinc blende InP and the corresponding parameter of wurtzite CdS.…”