Photoplastic effect and Vickers microhardness in III–V and II–VI semiconductor compounds

The influence of light illumination on the dislocation behaviour in GaAs and ZnS has been investigated by room temperature indentation tests in darkness and under illumination. It is shown that the photoplastic effect (PPE) can be evidenced by this technique providing: (i) small loads are applied to the indentor; and (ii) the illumination wavelength is close to the absorption edge of the semiconductor. Transmission electron microscopy studies indicate that: (i) in GaAs the negative PPE originates in an illumination induced increase of the mobility of α dislocations, due to non radiative recombination of excited carriers at dislocation sites; and (ii) in ZnS the positive PPE originates in an illumination induced increase of the Peierls stress.