STUDY OF THE EFFECTS OF CO2-LASER IRRADIATION ON CD0.204HG0.796TE

The behaviour of p-type Cd0.204Hg0.796Te used in IR detectors was stud ied under high power CO2 laser irradiation at room temperature. Its me lting threshold was determined for two irradiation conditions. (1) For a pulsed focused laser (pulse duration tau = 0.3 ms, spot diameter 22 5 mum), the melting threshold fluence ranged from 13 to 38 J cm-2. (2) For a continuous wave CO2 focused laser beam (spot diameter 240 mum, I = 360 kW cm-2) swept on the target using a rotating mirror, the thre shold fluence was F = 11 J cm-2, corresponding to a scanning speed of 8 m s-1. These experimental results were compared with calculated valu es assuming either a monodimensional model or a two-dimensional combin ed absorption and conduction model. The threshold calculated with the monodimensional model was F = 15 J cm-2, whereas the threshold calcula ted with the two-dimensional model was F = 19 J cm-2 for the pulsed ir radiation and F = 17.5 J cm-2 for the continuous irradiation. A decrea se in mercury concentration from 39.8 at.%) down to 13.1 at.%, dependi ng on the fluence, was observed using X-ray microanalysis.