Mechanical properties and photomechanical effect in GaP single crystals

Mechanical properdes of GaP single crystals have been investigated from 100° to 300°C by observing dislocation rosette patterns on indented specimen surfaces. It has been found that GaP has mechanical properties which are common to those of other III–V compounds or elemental semiconductors in several points: the {111} surface polarity dependence of microhardness, the mobility difference between α- and β-dislocations, and the conduction type dependence of dislocation mobility. The growth of dislocation rosettes is suppressed by baking specimens in air. Contrary to the case of II–VI compounds, illumination of visible light during indentation enhances the mobility of dislocations. These experimental results are discussed in terms of an effect of electronic charge of dislocation on its mobility.