Thermal recovery processes in laser irradiated HgCdTe (PC) detectors

An experimental method for measuring the transient and steady-state thermal characteristics of ir photoconductors is introduced. Thermal recovery processes in laser irradiated HgCdTe (PC) detectors were investigated. The characteristics of thermal recovery processes are found to be quite sensitive to the specific details of detector construction. For the most part thermal recovery in these detectors takes place on two separate time scales. Initially the signal recovers partially to an intermediate level on a time scale of several milliseconds. The rest of the recovery occurs much more slowly, i.e., on the order of hundreds of milliseconds. It was found that the magnitude of the thermally induced signal, the relative importance of the two recovery processes, and the exact shape of the thermal recovery curve vary with power density and irradiation time. A one-dimensional thermal model of the detector for both pulsed and cw laser irradiation is presented. Calculated thermal recovery curves are found to agree we l with the experimental results for irradiation times as long as 20 msec. The two recovery times are found to be due to the two thermally resistive bonding layers. The utility of this model for predicting the thermal characteristics of new improved detector designs is discussed.