Threshold of Inelastic Strain Formation in Si and GaAs Surface Layers under Multiple Pulsed Laser Irradiation

摘要

For the first time, a contactless local photoacoustic technique based on the spectroscopy of laser beam deviation was used to estimate maximal values of elastic shear strains φ_0 in micrometer-sized surface regions of Si and GaAs; the values obtained fall in the range of 10~(-5) < φ_0 < 10~(-4). The development of irreversible inelastic processes in the surface layers of semiconductors subjected to a series of focused laser pulses under photoinduced quasi-static strains φ > φ_0 is demonstrated. Studying the diffuse and Raman scattering of light near the thresholds φ_0 suggests that the early stage of the inelastic cyclic strain photoinduced in the surface layers is accompanied by the generation and spatial redistribution of point rather than extended defects (e.g., dislocations). A number of threshold values, such as the photoinduced in crease in the temperature and the mean shear stresses that appear in the surface layers of Si and GaAs samples exposed to local submicrosecond radiation, are estimated. The physical nature of the low-threshold effects is discussed.