Research On The Irradiation Effects Of PV-HgCdTe Linear Array Detector Under Laser

With the widespread use of infrared focal plane detector in different aspects,especially for industry and scientific technology purpose, more and more attentions arebeing paid to the irradiation effects of infrared devices. It is well known for theirradiation effects of the unit detector, such as carrier transport, chaos effect and thermaldamage model. However, less attention was paid to the irradiation effects of infraredarray detector with signal processing circuit. Therefore, it is of great practical importantto carry out the research on the irradiation effects of infrared array detector. Thisdissertation is focused on the irradiation effects of PV-HgCdTe linear array detector,whose structure is in common use. The theoretical and experimental studies are made onthe mechanism of several effects with PV-HgCdTe detector by continuous laser andultrashort pulse laser.1. The irradiation effect on the detector by continuous laser is studied. Thephenomena of the irradiated element’s saturation, supersaturation and Low-voltageoutput of light signal responds are observed. Besides, the results of experiments showthat the basal signal of the non-irradiated element overall respond as a whole, thevoltage value displayed firstly decreases and then raises with high noise. The results ofresearch show that the paradoxical responded phenomenon of irradiated cell is primarilycaused by the basal signal response of the device with CDS circuit in bright light andthe phenomenon of the non-irradiated cell is mainly caused by the public P polestructure of the linear array detector and the public Vrefvoltage structure of the circuit.2. Optical crosstalk of space between pixels in the linear array detector withdifferent structure and material parameters is studied, whose size is related to thestructure, temperature and material of the detector. The study shows that the thicknessof substrate’s epitaxial layer in the internal structure and the vacuum layer in theexternal optical structure are the major influencing factors for the amplitude of opticalcrosstalk. The size of optical crosstalk is8.7%, even if the maximum laser powerdensity in the experiment is not enough to cause all of the non-irradiated pixels’ outputsignal change greatly. It indicates that the optical crosstalk is not a major factor in thedetector.3. The irradiation effect on the detector by ultrashort pulse laser is studied.Experiments discover that the linear array detector performs three kinds of outputresponse characteristics that differ from continuous laser irradiation effect. Althoughkeeping the same irradiation position and irradiation intensity, the linear array deviceperforms multiple output responses to pulsed laser; With larger light intensity, theresponse of laser irradiation interferes the output signal of the linear array device whenwithout follow-up laser irradiation; Linear array device responds to pulse laser in reverse, accompanying with translation in cycle. Study shows that the variability ofpulsed laser irradiation time relative to the detector’s work sequence is responsible formultiple output responses phenomenon, and the main cause of interference effect is thatthe processing circuit can’t clear signal charge in time after laser irradiation. The reverseresponse of the linear array devices by ultrashort pulse laser irradiation may be due tothe negative photovoltaic response of the detection unit to picosecond laser, and cyclicalchanges of the laser irradiation time to the detector’s work sequence.The results of this paper has important guiding significance to the deepunderstanding and improvement of the performance of the linear array detector, whichis of importance for the further research in relevant fields.