Study of the effects of CO 2 laser irradiation on Cd 0.204Hg 0.796Te

Abstract

The behaviour of p-type Cd 0.204Hg 0.796Te used in IR detectors was studied under high power CO 2 laser irradiation at room temperature. Its melting threshold was determined for two irradiation conditions. (1) For a pulsed focused laser (pulse duration τ = 0.3 ms, spot diameter 225 μm), the melting threshold fluence ranged from 13 to 38 J cm −2. (2) For a continuous wave CO 2 focused laser beam (spot diameter 240 μm, I = 360 kW cm −2) swept on the target using a rotating mirror, the threshold fluence was F = 11 J cm −2, corresponding to a scanning speed of 8 m s −1. These experimental results were compared with calculated values assuming either a monodimensional model or a two-dimensional combined absorption and conduction model. The threshold calculated with the monodimensional model was F = 15 J cm −2, whereas the threshold calculated with the two-dimensional model was F = 19 J cm −2 for the pulsed irradiation and F = 17.5 J cm −2 for the continuous irradiation. A decrease in mercury concentration from 39.8 at.%) down to 13.1 at.%, depending on the fluence, was observed using X-ray microanalysis.