Electrical and photoelectric properties of p-cds/p-cdte/znte/zncds heterojunctions

Размещено на http://www.allbest.ru

Electrical and photoelectric properties of p-cds/p-cdte/znte/zncds heterojunctions

Elmira Alesgerovna Khanmamedova

Assistant, Faculty of information technology and control Azerbaijan State Oil and Industry University, Baku, Azerbaijan

Summary

Studies show that during thermal processing, major changes occur in p-CdS/p- CdTe/ZnTe/ZnCdS heterojunctions. The nature of the change in electrical and photoelectric properties of heterojunctions depending on thermal processing conditions shows that the volume charge layer expands due to the presence of acceptor levels near the surface of the Zn 1 -xCdxS layer (Fig. 1). Therefore, the capacity of p-n heterojunctions decreases. The increase in photoresponse across all spectra indicates that the compensation of donor-type natural defects with acceptor levels results in the formation of a high-resistivity layer in the near-surface layer and increases the rectification factor. Light absorption is more effective due to the high resistivity layer, which means that the utility of the absorbed beam and the accumulation of carriers with p-n heterojunctions are increased.

Keyword: semiconductor, photovoltaic effect, electrochemical precipitation methods, heterojunctions, depends, photoresponse, nanostructure.

thermal processing photoresponse

The chemically prepared p-CdS/p-CdTe/ZnTe/Zn1-xCdxS heterojunctions exhibit dominant tunneling currents even at a temperature of 270 К. It is possible to significantly reduce the tunneling current due to the improvement of the technology, firstly, the increase of the potential barrier through which the tunneling electrons pass, and secondly, the reduction of the concentration of centers in the transition. Electrons move from the conduction band of the wide-band material to the narrow band through the tunneling mechanism. Non-equilibrium electrons and holes appear during photoexcitation with quanta from the Zn1-xCdxS film's own absorption field[3]. The barrier field in the base region removes electrons, and holes are trapped near the junction of traps and recombination centers. The presence of such compensation centers with a large concentration is actually one of the main features of the considered heterojunction. The barrier field promotes electron collection in the space charge field; therefore, the positive charge distribution in Zn1- xCdxS changes significantly even at a slight level of photoexcitation, resulting in an increase in conductivity.

Figure 1. Photoresponse spectrum of p-CdS/p-CdTe/ZnTe/Zn1 -xCdxS heterojunctions. Thickness of Zn1 -xCdxS films, nm: 1 -200, 2-500, 3-800

Thus, the intensity of the electric field at the heterojunction boundary increases sharply. The short-circuit current directly depends on the spatial distribution of the electric potential, and this distribution is directly related to the concentration of electrons located in the traps. When shown in a sample of any image, its points are illuminated differently, which results in different concentrations of electrons, trapped and, accordingly, different deflections of the force zones in the space charge field. If shown to stop, the difference in electron concentration is maintained long enough to allow the heterojunction to be used as an optical information recording device. Reading this information is possible by scanning the sample with infrared light. [5,7] The use of infrared illuminations also allows for image erasure, so the sample must be illuminated with high-frequency, long-duration pulses. Then the sample is suitable for storing another image again. The recording and reading processes can be carried out significantly in time, but long storage is accompanied by thermal destruction of the traps, resulting in a gradual loss of optical information. When the sample is kept at a temperature of about 80K, it is possible to read the data within a few days. Increasing the storage temperature results in a faster release of a thermal hole into the valence band.

The p-CdS/p-CdTe/ZnTe/Zn1-xCdxS heterojunction can exist in two different states. One of them - the balance - has a low sensitivity to infrared light and allows you to get a low value of the short-circuit current. The other condition - non-balance - is highly sensitive to infrared light and gives a fairly high short-circuit current value[4]. The transition from equilibrium to non-equilibrium state is carried out under the illumination of short-wave light due to the trapping in the space charge region of the Zn1-xCdxS layer and the accumulation of non-equilibrium holes in the traps. The maintenance of the non-equilibrium state in the structure is determined by the size of the recombination barrier and stacking, as well as the process of hole emission from the traps.[8] After the elimination of short-wave illumination, the emission begins to play a key role in the current transition, so the release of the trapped charge leads to the reverse change of the barrier parameters and the transition of the structure from the non-equilibrium state to the equilibrium state. The emission intensity determines the rate and speed of this change in barrier parameters, and thus the short-circuit current. [1,2,3] Therefore, it is clearly important to know how the emission barrier parameters are affected after photoexcitation of short-wavelength light is stopped. Let's consider the possibilities of using such a system for recording optical images of various spectral compositions. The maximum effect is achieved at 450-520 nanometers (Fig. 1). Short-wavelength light is strongly absorbed in the core layer. Thus, the thickness of the Zn1 -xCdxS layer and the diffusion length of charge carriers in this material determine the photoexcited hole concentration near the space charge field [11,12]. Not all photogenerated electrons reach the space charge field, which results in a decrease in the rate of short-wave stimulation. A sharp decrease in the sensitivity of the sample in the short-wave range of the spectrum is due to the recombination of the resulting charge carriers in the volume of the Zn1-xCdxS layer, not reaching the space charge region in time, that is, absorption of light [6,9,10]. The decrease in sensitivity in the long-wavelength region indicates a decrease in the p-CdS/p- CdTe/ZnTe/Zn1 -xCdxS aggregation coefficient and the presence of adhesion centers in Zn1-xCdxS. To increase the sensitivity, it is necessary to reduce the thickness of the base layer or create an optical image on a thin CdTe layer part.

Conclution

The use of a wide-band amorphous ZnS layer as a buffer layer in the glass/ITO/ZnS/ZnTe/CdTe/ structure significantly improves all parameters of these structures as a solar cell, and makes the use of multilayer structures more superior and appropriate than the two-layer ITO/ZnTe/CdTe/ structures shows.

References

Jafarov M.A., Nasirov E.F. , Khanmamedova E.A. "Preparation of nanosized А2В6 Compound Multilayer Structures for Solar Cell " Universal Journal of Physics and Application 1(2): p.125-129, 2013 https://www.hrpub.org/download/201309/ujpa.2013. 010212.pdf.

H.M. Mamedov, M.Muradov, M.Jafarov, Z.Konya, A.Kukovecz, K.Kordas, S.I. Shah, V.J.Mamedova, Kh.M.Ahmedova, V.U.Mamedov, E.A.Khanmamedova. "Photo- and gas- sensitivity of heterojunctions c-Si/porous-Si/CdS" Journal of Low Dimensional Systems, v 1 (1), 2017, Baku State University. https://www.researchgate.net/publication/323280 578_Photo-_and_gas-_sensitivity_of_heterojunctions_c-Siporous-SiCdS.

R.G.Abaszade, A.G.Mammadov, V.O.Kotsyubynsky, E.Y.Gur, I.Y.Bayramov, E.A.Khanmamadova, O.A.Kapush, Modeling of voltage-ampere characteristic structures on the basis of graphene oxide/sulfur compounds, International Journal on Technical and Physical Problems of Engineering, Vol.14, №2, pp.302-306, 2022. http://www.iotpe. com/IJTPE/IJTPE-2022/IJTPE-Issue51 -Vol14-No2-Jun2022/37-IJTPE-Issue51-Vol14-No2- Jun2022-pp302-306.pdf.

R.G.Abaszade, A.G.Mamedov, I.Y.Bayramov, E.A.Khanmamadova, V.O.Kotsyubynsky, O.A.Kapush, V.M.Boychuk, E.Y.Gur, Structural and electrical properties of sulfur-doped graphene oxide/graphite oxide composite, Physics and Chemistry of Solid State, Vol.23, №2, pp. 256-260, 2022.

E.A.Khanmamedova, Effect of KOH + C3H8O texturing on the electrical Properties of p- Si/textured-Si/ZnS1-xSex heterojunctions Journal of Baku Engineering University PHYSICS 2019. Volume 3, Number 2, p146-150. http://journal.beu.edu.az/media/media/ files/Fizika_2019_2_Volume3_Number2.pdf.

E.A.Khanmamedova, Effect of etching on the electrical properties of ZnS1-XSeX/P-Si andZnSe1-XTeX/P-Si heterojunctions Journal of Low Dimensional Systems, v 3 (2), 2019, Baku State University. http://static.bsu.az/w10/Shekil/LOW%20Dimension%20Journal/

2019-2/LDS%20VOL3(2)%20(2)%20en%20son%201 .pdf.

E.A. Khanmamedova, Electrical and optical properties of ZnSTe thin films prepared by chemical bath deposition, 7th INTERNATIONAL CONFERENCE MTP-2021 :MODERN TRENDS IN PHYSICS, DECEMBER 15-17, 2021 BAKU STATE UNIVERSITY | BAKU, AZERBAIJAN. http://mtp2021 .bsu.edu.az/ABSTRACT_BOOK_MTP_2021.pdf.

E.A.Khanmamedova, Electrical and optical properties of structures formed on the basis of thin layers of different composition CdSe1-xSx, ECOENERGETiCS 19(1), 2022. pp. 101104. http://ieeacademy.org/wp-content/uploads/2022/06/Ecoenergetics-N2-2022-pape rs-1.pdf.

R.G. Abaszade photoconductivity of carbon nanotube obtained by arc discharge method, International scientific journal «Grail of Science» | No17(July, 2022), pp.248-250. https://archive.journal-grail.science/index.php/2710-3056/issue/view/22.07.2022/4.

R.G. Abaszade ,Synthesis and analysis of flakes graphene oxide, Journal of Optoelectronic and Biomedical Materials Vol. 14, No. 3, July - September 2022, p.107114. https://chalcogen.ro/107_AbaszadeRG.pdf.

S.R.Figarova, E.M.Aliyev, R.G.Abaszade, R.I.Alekberov, V.R.Figarov, Negative Differential Resistance of Graphene Oxide/Sulphur Compound, Journal of Nano Research Submitted, Vol.67, pp.25-31, 2021. http://dx.doi.org/10.4028/www.scientific.net/JNano R.67.25.

R.G.Abaszade, O.A.Kapush, S.A.Mamedova, A.M.Nabiyev, S.Z.Melikova, S.I.Budzulyak, Gadolinium doping influence on the properties of carbon nanotubes, Physics and Chemistry of Solid State, Vol. 21, No. 3, pp. 404-408, 2020.

Размещено на Allbest.ru