Research On The Irradiation Effects Of Insb Detectors Under Sub-band CW Laser

With the widespread use of photoelectric detectors in different aspects, especially for military and civil purpose, more and more attentions are being paid to the irradiation effects of semiconductor materials and photoelectric detectors. The spectrum of the photoelectric detectors ranges from ultraviolet to far-infrared since there are many kinds of semiconductor materials. However, for a specific detector, it could only response to a specific spectrum range. In other words, every kind of detector has a cut-off frequency, which is mainly determined by the band gap energy. Generally speaking, we call the laser above-band laser, whose photon energy is larger than the band gap energy; otherwise call it sub-band laser. It is well known for the irradiation effects of detectors by above-band lasers. However, the lasers which are adopted to disturb photoelectric detectors are probably sub-band lasers in many cases. Therefore, it is of great practical importance to carry out the research on the irradiation effects of photoelectric detectors under sub-band laser.This dissertation is focused on the irradiation effects of InSb detector, which has been widely used. Exploratory research is made on the mechanism of several effects with InSb detector.A new phenomenon is observed when a photoconductive InSb detector with 0.228eV band gap is irradiated by 10.6μm laser, whose photon energy is 0.12eV. The detector is heated by this sub-band laser, due to absorption of photons. A critical temperature T0 exists in this process. When the temperature of the detector, T, is lower than T0, the number of carriers changes little while the conductivity changes because of the change of electron mobility. The mobility decreases with the increase of temperature and varies as T-2.35. At T>T0, the concentration of thermally-activated carrier increases with temperature proportional to exp (-Eg/2k0T). As a result, the influence of carrier concentration becomes more and more important. As a result, the output of the detector decreases. In a word, the output voltage of photoconductive detector rests with the temperature dependence of mobility and concentration of carriers. This work provides an experimental basis for consummating the carrier transport model.We carry out experiments on photovoltaic detectors irradiated by sub-band lasers, and get the rules of dynamic responses. It is found that the voltage response of photovoltaic detector to sub-band laser is similar to that to above-band laser. The voltage response mechanism of photovoltaic detector under the irradiation of sub-band laser is analyzed. Comparing with the photovoltage and temperature difference-EMF (electric motive force), thermovoltage is the main mechanics of voltage response under sub-band laser irradiating. Exploratory research is carried out to investigate the influence of the concentration of initial free carriers to the output of photovoltaic detector under sub-band laser irradiation. A lower concentration of initial free carriers leads to a notable thermovoltage; otherwise, the build-in electric field will weaken and the response ability will decrease, due to the temperature rise induced by free carrier absorption.This dissertation is focused on the mechanism of the interaction between higher power sub-band laser and InSb detector, and find that out-band laser could disturb photoelectric detectors effectively. Besides, the simultaneity irradiation of sub-band and above-band laser could improve the absorption of sub-band laser, which could improve the disturb impact of sub-band laser.