INVESTIGATION OF THE SURFACE PREPARATION OF GAAS SUBSTRATES FOR MBE AND VPE WITH WHOLE SAMPLE OPTICAL REFLECTION

Surface properties and morphology of the mirror-like GaAs and GaSb substrate wafers for MBE and VPE growth were studied using whole sample optical reflection (''magic mirror'', or ''Makyoh'' phenomenon). Samples with various surface treatments were studied using this ''Makyoh'' method comparing the results with other methods such as X-ray diffractions, Nomarski pictures and surface roughness measurements. It has been found, that the generally used substrate etching procedure, prior to vapour phase epitaxy (VPE) and molecular beam epitaxy (MBE), affect differently the substrate originating from different crystal growth sources. It was shown that, in certain cases, the etching procedure could give worse surface flatness, than it was earlier. It is also shown, that Makyoh-type investigation can be used for selection of high quality substrates. However if certain damaged layers, containing precipitates and dislocations exist under the ''perfect'', outside mirror-like surface, they can not be detected by the Makyoh method.