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      Annotation. In this article, the rates of surface recombination in polycrystalline CdTe films obtained on oxidized substrates are studied, and the results of the action of corona discharge into the CdTe-SiO2—Si-Al structure are presented. In the static mode, a shift of the short-circuit current spectra to the short-wave region was observed. To analyze the displacement of the short-circuit current spectra, the microwave probe photoconductivity (MW-PC) method was used and contactless registration of transient decay processes for redundant carriers was performed. From the data obtained, it was found that the rate of surface recombination was estimated at 19 ns. It was determined that filling of surface traps in CdTe leads to a decrease in the effect of surface recombination.

      Keywords: semicrystalline structures, surface recombination rate, polycrystalline films, spectrum shift.

      Аннотация. В данной статье изучено скорости поверхностной рекомбинации в поликристаллических пленках CdTe полученных на окисленных подложках, Приведены результаты действия коронного разряда в структуру CdTe-SiO₂—Si-Al. в статическом режиме наблюдался смещение спектров тока короткого замыкания в коротко волновую область. Для анализа смещения спектров тока короткого замыкания использован метод микроволновой зондовой фотопроводимости (MW-PC) и проведена бесконтактная регистрация переходных процессов распада для избыточных носителей. Из полученных данных установлено что скорость поверхностной рекомбинации была оценена 19 нс. Определено, что заполнение поверхностных ловушек в CdTe приводит к уменьшению воздействия поверхностной рекомбинации.

      Ключевые слова: полукристаллические структуры, скорость поверхностной рекомбинации, поликристаллические плёнки, смещение спектров.

      CdTe semiconductor films are an important material for the creation of photodetector devices based on its heterostructures operating in the near (up to 3 microns) and far (8—14 microns) The IR range. This paper presents studies of the heterostructure obtained from growing CdTe on the surface of SiO2 – Si. This CdTe – SiO2 – Si heterostructure is interesting because using the built-in charge in the SiO2 layer, it is possible to control the PHOTOEMF and the short-circuit current spectrum.

      Polycrystalline CdTe films with a grain size of 0.05—0.1 microns were grown on a heated SiO2-Si surface in a vacuum of 105 mmHg. The photosensitivity of the resulting structure is controlled by the action of an electric field or corona discharge, which change the built-in field in the SiO2 layer. To enhance the effect, an Al layer is applied to the Si surface, and we get a «reverse» CdTe—SiO2—Si—Al type field effect transistor, where a control charge is located under the semiconductor layer, and its surface remains open.

      When the voltage between the Al layer and the electrode exceeds 6 kV, a corona discharge occurs, while the embedded field inside the structure reaches 100V. At the same time, at the boundary of the CdTe and SiO2 layers, charge carriers (electrons and holes) are tunneled from the semiconductor layer into the deep levels of the dielectric. Charge carriers in the film and at the interface, depending on the magnitude of the built-in charge, change the potential relief, therefore, when this layer is photoexcited, they will be generated under the influence of the built-in charge. This changes the distribution of current carriers generated on the surface in such a way that it draws them into an area that is accessible only to weakly absorbed electromagnetic radiation. Therefore, photoedics also occurs with long-wave excitation. Due to the asymmetry of the barriers, weak absorbed radiation also generates photoedcs of the reverse sign. Then, under the influence of the volume charge, the inversion of the photoedc sign will mix the short-wave region, and the photosensitivity increases in the region of the electromagnetic radiation spectrum we are studying.

      As stated above, when studying the effect of a corona discharge on the CdTe-SiO2—Si-Al structure, it showed that the short-circuit current spectra, depending on the magnitude of the external corona discharge in static mode, their displacement into the short-wave region was observed (Fig.1).

      Figure 1 shows the spectral dependences of the short-circuit current (Icz) of the CdTe layer for various values of corona discharge intensity, which were carried out by contact (2) and electric probe contact (3) to the surface of the CdTe semiconductor. It can be seen that in the absence of external influences in the Icz (v) spectra, an inversion of the Icz sign is observed in the vicinity of the light quantum energy value equal to hv= 1.21eV (curve 1) the inclusion of the surface corona discharge potential between the CdTe layer and silicon leads to a significant change in the spectral sensitivity of the short-circuit current (Icz). When the surface potential changes within its value from 0 to 100V, the inversion position of the short-circuit current sign will mix into the short-wave region of the spectrum. In this case, the maximum photo sensitivity of the Icz will be mixed into the short-wavelength region of the spectrum and in the range from 0.93 eV to 1.5 eV. The position of the maximum value of the Icz increases by more than 1000 times at = 70V (curve 3) [63; – p.22—25]. For a qualitative description of the physical nature of the transfer phenomenon occurring in the CdTe-SiO2-Si-Al structure (semiconductor – oxide – semiconductor, i.e. When a voltage is applied to it, consider a model in which a stationary current is a flow of electrons tunneling from the conduction band of a semiconductor into a deep level located in an oxide (including into a trap at the interface). Since the thickness of the silicon oxide in the structure under consideration is 0.4 microns, we estimate that the first contribution and the total flux are insignificant (less than 25%).

      It should be noted that during corona discharge, the activation energy of the deep level (0.7eV) changes significantly depending on the potential of the corona discharge. This change is due to the influence of the optical ionization energy of the deep level located in the region of the volume charge near the SiO2 layer (this is indicated by experimental results). If we consider that this change occurs due to the Poole – Frenkel effect [64; p.52], then the mixing of the level can be estimated by the formula

      where, is the dielectric constant of CdTe, e is the electron charge. Then, according to our estimates, the electric field strength in the vicinity of the defect reaches 103 V/cm.

      To verify and analyze the above, the CdTe layer was separated from the SiO2 surface and installed on the sapphire surface. After that, contactless registration of transient decay processes for excess carriers was carried out using the microwave probe photoconductivity (WPC) method [2]. The parameters of deep traps and the state of their filling are determined by the photoionization of the captured media. Photoionization took

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