Reaction with compound semiconductors

Here we describe some of the results. In each of these studies, the compound semiconductor was first etched in either acid or base to remove the oxide. The specific surface groups following the etch are not well understood. However, Pluchery et al. have followed the acid etching of InP by in situ infrared spectroscopy [175] and observed the removal of the oxide. Unlike Si, for which an acid (HF) etch leaves the surface hydrogen-terminated and temporarily passivated, acid etching of InP does not produce a chemically passivated surface. Presumably, the surface is left unprotected, and quickly oxidizes if not passivated by another process. Similar results showing reduction or removal of the oxide are seen for GaAs [174,176,177]. 

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Metallic Antimonides. Numerous binary compounds of antimony with metallic elements are known. The most important of these are indium antimonide [1312-41 -0] InSb, gallium antimonide [12064-03-8] GaSb, and aluminum antimonide [25152-52-7] AlSb, which find extensive use as semiconductors. The alkali metal antimonides, such as lithium antimonide [12057-30-6] and sodium antimonide [12058-86-5] do not consist of simple ions. Rather, there is appreciable covalent bonding between the alkali metal and the Sb as well as between pairs of Na atoms. These compounds are useful for the preparation of organoantimony compounds, such as trimethylstibine [594-10-5] (CH2)2Sb, by reaction with an organohalogen compound. 

Mg(THF), when the stoichiometry was 1 2. Monomeric and dimeric amidinate complexes of magnesium have been studied in detail with respect to potential applications of these compounds in the chemical vapor deposition of magnesium-doped Group 13 compound semiconductor films. The reactions and products are summarized in Scheme 16. ... 

The induced co-deposition concept has been successfully exemplified in the formation of metal selenides and tellurides (sulfur has a different behavior) by a chalcogen ion diffusion-limited process, carried out typically in acidic aqueous solutions of oxochalcogenide species containing quadrivalent selenium or tellurium and metal salts with the metal normally in its highest valence state. This is rather the earliest and most studied method for electrodeposition of compound semiconductors [1]. For MX deposition, a simple (4H-2)e reduction process may be considered to describe the overall reaction at the cathode, as for example in... 

Fig. 3.16 Reaction schemes of different CBD mechanisms for compound semiconductors (a) atom-by-atom process (b) aggregation of colloids and (c) mixed process. (Reprinted from [247], Copyright 2009, with permission from Elsevier)...

In the first chapter, on electrochemical atomic layer epitaxy, Stickney provides a review of experimental methodology and current accomplishments in the electrodeposition of compound semiconductors. The experimental procedures and detailed fundamental background associated with layer-by-layer assembly are summarized for various compounds. The surface chemistry associated with the electrochemical reactions that are used to form the layers is discussed, along with challenges and issues associated with device formation by this method. 

The oxide redox energy levels for all elements except gold are cathodic to the redox level of the H2O/O2 couple. Gold, however, is an impractical component for compound semiconductors. All other compound semiconductors employed as electrolysis photoanodes will undergo surface oxidation in aqueous electrolytes to produce a surface oxide film which normally constitutes the stable surface of the photoelectrode. Our proposed mechanism indicates that the proton induced oxide dissolution reaction arises from product ir ion interactions with the oxide anion (0=). 

The second topic of this chapter is the role of coordination compounds in advancing electrochemical objectives, particularly in the sphere of chemically modified electrodes. This involves the modification of the surface of a metallic or semiconductor electrode, sometimes by chemical reaction with surface groups and sometimes by adsorption. The attached substrate may be able to ligate, or it may be able to accept by exchange some electroactive species. Possibly some poetic licence will be allowed in defining such species since many interesting data have been obtained with ferrocene derivatives thus these organometallic compounds will be considered coordination compounds for the purpose of this chapter. 

Silicon Dioxide. Si02 layers produced by PECVD are useful for intermetal dielectric layers and mechanical or chemical protection and as diffusion masks and gate oxides on compound-semiconductor devices. The films are generally formed by the plasma-enhanced reaction of SiH4 at 200-300 °C with nitrous oxide (N20), but CO, C02, or 02 have also been used (238-241). Other silicon sources including tetramethoxysilane, methyl dimethoxysilane, and tetramethylsilane have also been investigated (202). Diborane or phosphine can be added to the deposition atmosphere to form doped oxide layers. 

In this paper our results to simulate the photoactive semiconductor/ electrolyte interface in UHV by adsorbing halogens and H20 on semiconductor surfaces are described. For these experiments layer type compounds and ternary chalcogenides have been considered because clean faces can easily be prepared by cleaving the crystals in UHV and because the reactions with halogens are intensively studied for photoelectrochemical solar cells. 

In the present paper the reaction of some elemental and compound semiconductors with aqueous solutions will be considered in relation to their surface structure. The influence of their semiconducting nature will be discussed where it is of significance. This paper is based primarily on work on germanium and HI-V compounds performed at die Lincoln Laboratory of M. I. T. over the last few years. 

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