The Defect Structure of GaP Crystals Grown from Gallium Solutions, Vapor Phase and Liquid Phase Epitaxial Deposition

Abstract

The defect structure of normalGaP crystals grown from gallium solutions, vapor phase and liquid phase epitaxial deposition is described. Etchants have been used to demarcate emergent dislocations, stacking faults, and p‐n and n‐n+ junctions. Crystals grown from gallium solutions are inhomogeneous with respect to defect structure and contain substantial dislocation‐free regions. Evidence is cited which indicates that some dislocations are introduced during growth whereas others are apparently generated at high stress regions during cooling. It is demonstrated that vapor phase epitaxial deposition on normalGaP substrates is capable of yielding nearly dislocation‐free crystals containing no stacking faults. The high density of defects observed in crystals grown on normalGaAs substrates is attributed to the heteroepitaxial mode of growth, in particular, the difference in thermal contraction of the growth layer and substrate on cooling from the growth temperature. normalGaP diodes fabricated by liquid‐phase epitaxy, in contrast to those formed by vapor‐phase epitaxy, do not contain interfacial dislocations at the growth‐substrate interface, i.e., p‐n junction.

Reduced Dislocation Densities in Liquid Phase Epitaxy Layers by Intermittent Growth

“…Crystals grown by these methods generally contain fewer dislocations than the substrates upon which they are grown. This improvement in crystalline perfection has been observed by etch pit or x-ray topography techniques in GaP (4,5), GaAs (6), and GaSb (7,8). The reported reduction in dislocation density p is typically by factors in the range of 3-10, and in all cases the reduction is abrupt, occurring at the initial growth interface.…”

“…Successive step reductions in p were attempted using a cooling cycle with four interruptions, with a 10-min thermal arrest between each growth increment. 4 The temperature range for each interval (see Table II) was chosen to give incremental layers of approximately the same thickness. Four nearly equispaced junctions were observed on the etched cleavage-face of a crystal grown in this manner.…”

“…(where x2 and xl are the atomic ratios of lithium in solution) up to about 2 a/o lithium, whereas at higher concentrations the departure from pure Nernstian behavior is no longer negligible. A very general equation for the emf of cell [4] might be obtained when considering cell [4] as a double cell, with the intermediate electrolyte acting as a gas-tight diaphragm, so that the oxygen pressures above both solid solutions are those corresponding to the stoichiometry. With the electrolyte working as a pure lithium conductor, the emf of a single cell Pt (02), Li20 (a)/~-Li2SO4/Li could be written…”

Gallium Phosphide Double-Epitaxial Diodes

“…But as Saul (15) has recently shown, SG platelets are largely dislocation free, which makes this supposition unlikely. One might suppose that further reduction of dislocations by the double growth step would produce more perfect junctions.…”

A kinetic study of structured surface relief patterning of GaP $$(\bar 1\bar 1\bar 1)$$

“…Anisotropic etching of III-V materials is a key enabling technology for many devices and has been documented in a number of excellent reviews and monographs. 11,12 Only a few etchants have been used for orientation dependent etching of GaP, for example H 3 PO 4 on (111), ( 1 1 1 ), and (100) oriented Au-masked GaP wafers, 13 1.0 M K 3 Fe(CN) 6 -0.5 M KOH on (111) and (100) orientated SiO 2 or Ti-masked GaP, 14 and 3 M NaOH for (111) and ( 1 1 1 ) orientated GaP. GaP is an excellent material for high temperature optoelectronic devices as well as radiation hard devices.…”