Balaban A. Relaxation processes in image sensors on the basis of nonideal CdS-Сu2S heterojunction

The dissertation is dedicated to a definition to the mechanism and to building of relaxation processes model in CdS-Cu2S heterojunction, which is to be elaboration image sensors. Two phases of nonequilibrium charge relaxation in a space-charge region were defined: a phase of a fast relaxation and a phase of a slow relaxation. It is shown, that the first phase is realized due to a charge release by tunneling to surface states of heteroboundary; the second - due to thermal release of localized charge. It is shown, that the effect of short-circuit currents modulation by means of short-wave illumination is realized by means of monotype deep capture centers for holes in wide-band-gap CdS semiconductor. It is established, that the saturation of a CdS-Cu2S heterojunction signal at increasing of intensity of short-wave illumination occurs due to the considerable excess of carriers drift velocity which cross heteroboundary, over a velocity of a surface recombination. Expression for the characteristic curve of nonideal CdS-Cu2S heterojunction sensor is obtained. This expression is in good agreement with experimental data and may be used for examination of sensitometric characteristics of similar devices. Obtained results can be used for a description of signal relaxation of an investigated sensor and for consideration of processes and phenomena in typical nonideal heterojunctions. Materials of dissertation also may be applied at instrument making industry for creation of efficient image sensor on the basis of nonideal heterojunctions.