THE INFLUENCE OF LASER RADIATION ON THE OPTICAL PROPERTIES OF THIN NEAR-SURFACE LAYERS OF SEMICONDUCTORS

Abstract

Optical studies of the reflection spectra of n-Si(100) single crystals with a resistivity of ρ = 5 Ω∙cm; n-GaAs with a resistivity of ρ = 10 Ω∙cm; CdTe (111) with a resistivity of ρ = (2÷5)∙109 Ω∙cm; Cd1-хZnxTe (x=0.1) solid solutions with resistivity ρ = (5÷30)∙109 Ω∙cm in the spectral range (0.2-1.7)-10-6 m before and after laser irradiation in the energy range 66 mJ/cm2-108 mJ/cm2 for n-Si (100) and n-GaAs (100), in the energy range of 66 mJ/cm2 - 164 mJ/cm2 for CdTe(111), in the energy range of 46.6 mJ/cm2 - 163.5 mJ/cm2 for Cd1-хZnxTe (x=0.1) solid solutions. An increase in the reflectivity of single crystals of n-Si (100), n-GaAs (100), p-CdTe (111) and solid solutions of Cd1-хZnxTe (x=0.1) under this laser treatment was experimentally observed. This integral effect is explained by the differences in the optical characteristics of the near-surface layer and the material volume (the complex refractive index of the near-surface layer differs from the complex refractive index of the material volume). The obtained spectra of optical reflection of the samples show that laser-stimulated interaction of impurities and defects occurs during irradiation, which leads to the formation of neutral complexes and a decrease in the intensity of impurity scattering processes. Experimental studies have shown that the main mechanism of pulsed laser irradiation influence on the optical properties of thin surface layers of the studied crystals is structural heterogeneity, i.e. absorption due to the presence of semiconductor sites with defective structure and the ability to actively absorb point defects and bind impurities. In silicon, the role of a heter is played by the surface layers of SiOx, SiO2, Si3N4, SiO2-xP, SiC and others; in gallium arsenide, by Ga2O3, As2O5 and others; in p-CdTe (111) single crystals and Cd1-хZnхTe (x = 0.1) solid solutions, the role of a getter is played by cadmium, tellurium, zinc oxides and their complexes.