<title>Transient electronic processes in MIS-photo targets of vidicons sensitive to midband infrared radiation</title>

Abstract

There is analytic investigation of electronic processes in vidicon photo targets on the base of metal-insulator-semiconductor (MIS) structures sensitive to middle band of infra-red (IR) radiation. The opportunity of working temperature regulation in vidicon photo targets sensitive to middle band IR radiation is examined at the expense of creation nonequilibrium abandoned area in MIS-structure.The problem of vidicon photosensitivity in the middle band of IR radiation at technically acceptable cooling temperatures remains urgent for television engineering. The certain successes in this direction are achieved with use in vidicon phototargets impured semiconductors and pyroelectrics [1]. However, the sensitivity of such vidicons is unsufficient for creation of a lot of systems of supervision. Higher photosensitivity in a mode of accumulation have the phototargets on the basis of MIS-structures with narrow gap semiconductors (InSb, InAs) in the field of own absorption. Such phototargets have the following structure [2,3]. The high-resistance photosensitive layer (epytaxial film with free charge carriers concentration about 1 O141 015 sm3) is located on the low-resistant semiconductor substrate (alarm plate). Final covering layer is a high-resistance semiconductor (for example CdS, CdTe) canying out a role of semiconducting dielectric layer on which surface the electronic beam scans. The semiconductor with electronic conductivity with completely activated impurities is used.Dielectric should have some conductivity for flowing out of the induced charge after reading the first staff of the image and preparation for recording the next one. The size of its resistance is chosen from condition of a commensurability of time of accumulation of the staff (TN) and time flowing out of a residiual charge (Maxwell relaxation time tM =c /4iu; for TN =1 02s value of -10 10M1 SM1).In structure the nonequilibrium abandoned mode is used. There is an accumulation of photocarriers during time of existence of abandoned area [4] .At scanning by an electronic beam on an insulator surface is put a charge creating a difference of potentials relatively of a low resistant substrate. An abandoned area of thickness about 1 -1 0 microns in the epytaxial layer becomes sensitive to IR under this difference of potentials. At presence of the entrance image in the covered sites due to accumulation of photocarriers and shielding by them of an external field the thickness of abandoned area becomes less than in blacked out and the charging relief of the image is formed in the structure. This relief is stored until! for the account of thermo-and photogeneration the number of electron-hole pairs sufficient for complete shielding of an electric field on all the area of the ructure under insulator is not formed.The interrogation of the relief is carried out at repeated passage of an electronic beam on a difference of recharging currents from the covered and blacked out sites.The theory of transients in such structures is in detail considered in [4, 5] with r...