Current Density-Anodic Potential Curves of Single Crystal GaAs at Low Currents in KOH

Current voltage curves and the effective dissolution valence have been determined for GaP electrodes in 3N NaOH solution. At electrode potentials of a few volts the current density for p-type (NA ~ 4(10)17-cm-3) is a factor of 10 4 greater than for n-type (ND ~ 4 (10)17 cm-3) electrodes. This difference allows selective removal of p material from p-n structures. Application of this selective etching to the fabrication of mesa structures for GaP light emitting diodes, and to junction delineation, is discussed. At large current densities, 6 charges are transferred per dissolved GaP molecule in distinction to the 3 transferred charges found previously in alkaline solution at low (< 2mA cm -~) current densities.As III-V compound semiconductor device technology is advanced, it becomes desirable to apply some of the electrochemical processing and evaluation techniques which have proven useful for silicon and germanium (1-3) to those materials. The present paper discusses anodic dissolution and selective etching of gallium phosphide.In comparison to germanium and silicon, the electrochemistry of the III-V compounds has not been widely studied. The occurrence and nature of surface films (4, 5) and the morphology of the etched surface (5, 6) have been determined for InSb. Several authors have discussed the electrochemistry (7-12) and Nuese and Gannon have described selective etching (13) of GaAs. Memming (14, 15) has studied GaP, but not at the rather large anodic current densities desired for etching and shaping operations.Experimental Current density-potential relations were determined in the apparatus of Fig. 1. The electrolyte was 3N aqueous NaOH maintained at 20~ although the exact temperature is not critical. Measurements were made in the dark and potentials are relative to the saturated calomel reference electrode. The samples were of (111) orientation, and both the Ga (111) and P-(lil) faces were studied. The faces were distinguished by their chemical etching characteristics in C12 saturated methanol. This and equivalent techniques are ultimately traceable to x-ray evidence. N-type samples were Se doped and p-type samples were Zn doped to a level of about 4(10) 17 cm -8 and were cut from LEC (Liquid Encapsulated Czochralski) pulled ingots. Ohmic contacts on p-type (n-type) were prepared by evaporating and alloying gold containing 1% Be (2% Si). Surfaces were chemically or mechanically polished, as applicable, before use as electrodes. The number of electronic charges passing through the external circuit per dissolved atom was determined by integrating the current for a certain time and measuring the weight loss with a microbalance.

Section: Resultsmentioning

confidence: 91%

mentioning

confidence: 99%

Anodic Dissolution and Selective Etching of Gallium Phosphide

Meek¹,

Schumaker²

1972

“…The chemical and anodic dissolution reactions occurring on various planes of III-V semiconductors in several electrolytes have been studied by Gatos et al (1,2), Pleskov (3), Dewald (4), Gerischer (5, 6), Harvey (7), Straumanis et al (8,9), and others. Dewald attempted to explain why the {111} inverse faces of InSb in an aqueous solution of KOH behave differently.…”

mentioning

confidence: 99%

The Anodic Dissolution Reaction of InSb: Etch Patterns, Electron Number, Anodic Disintegration, and Film Formation

Straumanis

1971

Self Cite

The etching behavior of the inverse {111} planes of undoped, semiconducting, n-type, InSb single crystals was explored. Depending upon the etchant, including anodic dissolution, various etch patterns were obtained on the inverse planes. In general the etch pits on the In{lll} plane were round, and the face was shiny, whereas the face of the inverse plane was dark and rough. The rates of dissolution in the electrolytes used were very low, especially in absence of oxidizers. The components dissolve as In 3 + and Sb 3+. At current densities above 40 or 60 mA cm -2 (on Sb{-1]]} or In{ill}), growth of a black, collodial film of Sb405C12 containing very fine metallic Sb particles occurs on both planes. The Sb particles result from the partial disintegration of InSb. Upon heating the film in vacuum, recrystallization occurs and the Sb aggregates to form larger particles. An explanation is offered for the different behaviors of the inverse {111} planes.

“…As usual, all variables have to be evaluated at susceptor temperatures. In normal practice, equations such as [30]-[32] are very inconvenient and difficult to handle, but it can be shown easily that in the limits of very small and of very large values of ~1, i.e., for very small and very large values of kz, the rate constant of the back reaction, one regains the rate expressions In general one can prove that reaction rates calculated from expression derived with model 2 will not differ more than about 20% from rates computed by means of model 1. Figure 7, e.g., shows the maximum ratio of deposition rates (model 1/model 2) for case 1, 82 = 82 as a function of 82 ~r P. In this case the difference between the two models is even smaller than 6%.…”

Section: Solutionsmentioning

confidence: 99%

Chemical Boundary Layers in CVD: II . Reversible Reactions

Croon

Giling

1990

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