Electrochemical, photoluminescence, and surface studies of the passivation of surface recombination processes on chemically treated gallium arsenide surfaces

Author: Lunt, Sharon Ruth

Year: 1992

Degree: Dissertation (Ph.D.)

Advisor: Lewis, Nathan Saul

Committee Member: Unknown, Unknown

Option: Chemistry

DOI: 10.7907/x6vc-m765

Abstract

This thesis describes work that has been done to study the chemical properties of GaAs surfaces relating to recombination processes. A variety of electrochemical, photoluminescence, and surface techniques have been used to study the mechanism an chemistry of the reduction of surface recombination in GaAs exposed to transition metal ions and complexes, and GaAs exposed to sulfur-containing molecules.

Electrochemical studies done on polycrystalline n-GaAs/liquid junctions treated with a variety of transition metal ions to study the mechanism of the observed improvement in I-V properties of GaAs(M3^(+))/Se^(-/2-)-KOH photoelectrochemical cells showed that the primary route is electrocatalysis. X-ray photoelectron spectroscopy (XPS) and extended x-ray adsorption fine structure (EXAFS) studies were performed on single crystal GaAs with Co, Ru and Cr ammines in order to determine the surface binding chemistry of the transition metals.

Steady state and time resolved and photoluminescence studies were done on GaAs surfaces exposed to sodium sulfide and a variety of organic thiols, alcohols and ammines. Unlike the transition metal ions, these types of complexes are shown to affect the cross section of surface recombination sites as determined by photoluminescence experiments. XPS studies were also done to correlate the observed changes in photoluminescence yield and lifetime with changes in surface chemistry.

Finally, some work has been done on an entirely different semiconductor system in order to explore the surface reactivity of a semiconductor surface at a more fundamental level. Several different types of metal dichalcogenides were exposed to strong Lewis acid complexes, and the surface chemistry was followed by XPS. These studies showed that there is a marked difference in the reactivity of metal dichalcogenide surfaces, which can be predicted from the known electronic structure of the conduction bands.

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