Study On Response Mechanism Of Element Photoelectric Detectors Irradiated By CW Laser

With the widespread use of photoelectric detectors in different aspects, especiallyfor military and civil purpose, more and more attentions are being paid to the irradiationeffects of semiconductor materials and photoelectric detectors. There are kinds ofphotoelectric detectors. However, for a specific detector, it could only response to aspecific spectrum range. In other words, every kind of detector has a cut-off wavelength.In the practical photoelectric confrontation, the lasers, which are adopted to disturbphotoelectric detectors, are probably not in the spectrum range of the photoelectricdetector. In this paper, we call the laser above-band gap laser, whose photon energy islarger than the band gap energy; otherwise call it sub-band gap laser.In this paper, the photovoltaic (PV) detectors and photoconductive (PC) detectorshave been taken as the investigated subjects. The nonlinear response mechanisms of PVdetectors under above-band gap laser radiation and response mechanisms of PCdetectors under sub-band gap laser radiation are carefully investigated. The investigatedcontents are as follows:1. The dynamic response physical process of PC detectors under above-band gaplaser radiation is investigated. The above-band gap laser irradiates the PC InSb detectorsin experiment. The carrier transport model of PC detector under above-band gap CWlaser radiation is established. The calculation results agree well with the experimentalresults. The response mechanism of PC detector under CW laser radiation is analyzed.It’s shown that the response mechanism of PC detector under above-band gap laserradiation is composed of optical excited carriers and thermal effects. The thermal effectsinclude temperature-dependence mobility effect and temperature-dependence carrierconcentration effect. When the voltage signals of PC detector under above-band gaplaser radiation are analyzed, the above three effects must be considered.2. The nonlinear response physical mechanisms of PV detector under above-bandgap laser radiation are carefully investigated. Based on many experimental results, theregular phenomena of PV detector under intense light radiation and specific phenomenainduced by individual difference are definite. Two typical over-saturation processes arediscovered and investigated. In theory, the generation conditions of the two typicalover-saturation processes are analyzed from the equivalent circuit model. The numericalcalculation model is established, and the two kinds of over-saturation processes arenumerical simulated. The numerical results and experimental results are in goodagreement. It’s shown that two generation mechanisms of the over-saturationphenomena of PV detector under above-band gap laser exist. One is increased darkcurrent due to thermal effect. The other is leak current due to intense light radiation. Theleak current is caused by the bugs, which are formed during the preparation process. 3. The dynamic response physical process of PC detectors under sub-band gaplaser radiation is investigated. In experiment, two typical infrared detectors (PC InSband HgCdTe detector) are taken in the sub-band gap laser radiation experiment. A newphenomenon, which universally exist in the experiments of PC detectors under sub-bandgap laser radiation. The generation mechanism of the new phenomenon is thoroughanalyzed. The carrier transport model of PC detector under sub-band gap laser radiationis established. The voltage response mechanism of PC detector under sub-band gaplaser radiation is analyzed. The numerical results and experimental results are in goodagreement. It’s shown that PC detector can response to the sub-band gap laser and theresponse mechanism is only thermal effect. The thermal effects are composed oftemperature-dependence mobility effect and temperature-dependence carrierconcentration effect. The temperature of the detector increased during the sub-band gaplaser radiation process. A critical temperature T0exists in this process, which istemperature corresponding to the minimum of the electrical conductivity.When thetemperature of the detector, T, is lower than T0, the dominant mechanism istemperature-dependence mobility effect. The output voltage signals increase with thetemperature. When the T is higher than T0, the dominant mechanism istemperature-dependence carrier concentration. The output voltage signals decrease withthe temperature. The output voltage signals of the detector are decided bytemperature-dependence mobility effect and temperature-dependence carrierconcentration effect.4. The response mechanism of PV detector under sub-band gap laser radiation isinvestigated. It’s shown that the dominate response mechanism of PV detector undersub-band gap laser radiation is thermovotage. The influence of output voltage signalswith different initial open-circuit voltage is analyzed. The Si solar cells are used toreproduce the experimental results of HgCdTe detector under sub-band gap laserradiation. The experiments are designed to demonstrate the existence of thermovoltage,the difference and relationship of thermovolatge and photovolatge, and the difference ofthermovoltage and thermoelectric voltage. The trueness of thermovolatge isdemonstrated from experiment.