On the Optical Memory of a Thin-Film pInSb-nCdTe Heterojunction Obtained by Laser Pulsed Deposition

Abstract

Thin film pInSb-nCdTe heterojunctions (HJs) were produced using pulsed laser deposition (PLD) technique and their photoelectric properties were studied for various thickness of the CdTe layer at nitrogen temperature and under a background radiation the photo-EMF for which was around 1.5 mV. At radiative excitation of the HJ a photo-EMF is observed, which persists when the excitation is turned off. The optical memory (OM) effect is observed in an idling regime and in a wide spectral range: (0.37–1.37)μm with “recording” (0.37–0.575)μm, (0.75–1.37)μm, and “clearing” (0.575–0.75)μm sub-regions. The maximum OM signal is observed at λ=0.575μm while the minimum is at λ=0.768μm. In the spectral dependence of the OM signal at direct and reverse scanning of monochromatic irradiation an hysteresis is observed which is evident for the OM effect. The time dependence of OM signal is investigated at λ=0.575μm and at various intensities of the radiation source. Here, an effect of saturation is clearly observed, and the time during which the OM signal runs up to saturation, depends strongly on the incident light flow power and decreases drastically as the latter is increased. The external bias applied to the HJ enhances the OM on 2 orders over its value in the idling regime. The OM signal persists for a time period no less than 105 sec, either with or without an external bias. The actually obtained values of “recording” sensitivity and the “recording” time are U=0.66 μJ/mm² and τ=10⁻⁴ sec., respectively. The OM signal reaches its maximal value as the thickness of CdTe layer increases (up to d=0.45 μm). It is shown that the investigated HJ possess the property of integration of the radiation.