Research Of The Boundary Of The Section Of A Photo Receiver Based On Mos pCdTe / CdO Structures

In this work, we investigated an intermediate layer in the structure of a photosensitive MOS structure nCdO / pCdTe . X-ray phase analysis shows that the intermediate layer between Mo and pCdTe is rather complex in composition. It contains dichalcogenides - three oxide MoO 3 and a thin layer of a composite material with the composition of ditelluride MoTe 2 . According to X-ray diffraction measurements, the total thickness of the intermediate layer is no more than ~ 200Ǻ. It was shown that in the nCdO / pCdTe structure the base material CdTe mainly consists of a homogeneous cubic modification layer


INTRODUCTION
Compounds А2В6 possess a successful combination of electrical and photoelectric properties, high photosensitivity , ability to electroluminescence, high thermal and radiation resistance, and a fairly simple technology for producing large-area films . Among the А2В6 compounds, cadmium telluride ( CdTe ) stands out for its electro physical, optical and photoelectric properties, as well as the possibility of obtaining oriented The American Journal of Applied Sciences (ISSN -2689-0992)  [2][3][4], which can significantly affect the output parameters of the structure. In this case, the atomic and electronic structure of the metal significantly affects the physicochemical processes occurring at the interface: metalsemiconductor. Since the interaction between a metal and a semiconductor is determined not only by the type of chemical bond of the semiconductor, but is largely determined by the structural -morphological characteristics of a thin metal layer. As a result, they affect the intensity of diffusion processes and phase formation in the transition layers in the diode structure. Therefore, the study of the real structure of photosensitive structures is not only of fundamental scientific, but also of practical interest.

SAMPLES AND RESEARCH METHODS
Films of p CdTe were obtained on a Mo substrate at a temperature T n = 620 0 C and a source T n = 950 0 C and a hydrogen rate H 2 VH2 = 2 liter / h. Metallographic studies of the film surface showed that the film consists of blocks of micro crystals with a thickness of 20-60 μm. At T n = 620 0 С ( T u = const , V H2= const ), the obtained CdTe films have a shiny surface with an excess of tellurium Te on the surface . And ssledo Bani show that during the synthesis largebloc polycrystalline CdTe films due re evaporation volatile component Cd in a gas phase system produces free tellurium atoms Te , which interact with the residual oxygen in the reactor to form a thin high-resistance layers Those O2 between a layer of p CdTe and n -CdO . The TeO2 oxide layer passivity's surface states in grain boundaries [5][6][7], which leads to a decrease in surface recombination and a significant increase in the lifetime of no equilibrium charge carriers to several tens of microseconds [8].
In order to elucidate the real structure of the MIS structures of nCdO / pCdTe , X-ray phase analysis was carried out on a DRON-2 setup ( Cu -radiation, Ni -filter). The information depth in this case is 1-2 µm.
To study the structure of the Mo -CdTe interface, the cadmium telluride film was separated from the molybdenum substrate and the surface of the film adjacent to the substrate and the substrate adjacent to the film was studied separately.
It was found that the initial high-purity molybdenum substrate does not contain oxides on its surface. Oxide -dichalcogenides trioxide MoO3 and MoTe 2 appears in The American Journal of Applied Sciences (ISSN -2689-0992) the process of synthesis, as a result of the contact of a heated molybdenum substrate as a result of chemical interaction with residual oxygen O 2 in the system [ 9 , 10 ].
Films pCdTe had a resistivity   5  7   with m and minority carrier lifetime of the order of τ = 10 -7 -10 -6 s . The thickness of the p CdTe films was ~ 30 µm . The grain sizes of polycrystalline pCdTe are in the range from 100 to 150 µm ; the grains cover the entire thickness of the film. For transparent th layer I Cd O was used magnetron sputtering method [ 11,12 ] .If dusting layer I as a target are used, respectively, pure cadmium C d .
Thickness CdO was 120 ÷ 150 nm. In a vacuum installation VUP -5M deposited thin films CdO by magnetron sputtering at a constant rated current at a substrate temperature of 300°C . Method thermal vacuum evaporation deposited Ш -shaped upper ohmic contact of indium In a thickness of 50 nm by vacuum deposition with an area w of S ≈ 6 mm 2 to S ≈ 1 cm 2 . Such a structure had a reverse current of ~ (2  ) · 10 -9 A and a rectification coefficient k = I p / I arr = 10 3 ÷ 10 4 (at V = 10 V) . To clarify the real structure of the nCdO / pCdTe structure , X-ray phase analysis was also performed. The information depth was 300 nm .
Results And Their Discussion. X-Ray Structural Analysis.
The lattice parameters of CdTe are calculated by the formula e and the Wolfe -Bragg formula : Wherein,  -Breggovsky angle determined by radiographs s index Miller.  was: 6.485 Å, 6.486 Å, 6.487 Å. The relative calculation error was 0.062, 0.077, 0.093%, respectively. The crystallite size increases to 1-2 µm and has a pronounced triangular shape, characteristic of the cubic phase modification ( Fig. 2 ) . Activation analysis [ 1 ] and Auger measurement -spectroscopy [ 13 ] show that the films telluride cadmium is composed of cubic-type portions spalerita modifications (Table.1).The results of X-ray structural analysis of the nCdO / pCdTe structures in comparison with the data and work [7] are presented inTable 1. CdTe films. On diffract gram (Fig.3) clearly distinguished reflexes Bragg angles corresponding essentially telluride cadmium cubic modification and compounds nCdO . The X-ray diffraction pattern shows that CdTe films ar e synthesized in the crystallographic directions (111), (220), (311), (400). Similar X -ray diffraction data were also obtained by the authors of other works, in which the films were grown by methods of electrod epositing [14], laser vapor deposition [15], and sublimation in a closed volume [16]. Reflexes with indices ( 1 1 1 ) i n t h e r a d i o g r a p h are the most intense. This means that this plane or ients the structure of the CdTe films as sphalerite. The presence of other peaks with r eflections (220), (311), and (400) indicates that the CdTe films have a cubic face -centered lattice with a coordination number of 12 [ 5,6 ]. The results of the indexing and fingerprinting comparison with the set of standard X -ray diffraction patterns ASTM [7] show that the grown CdTe films of the cubic modification are homogeneous. This also confirms the calculated Miller indices: 6.486 Ǻ , 6.485 Ǻ and 6.487 Ǻ according to the formula N = h 2 + k 2 + l 2 for three large peaks in the X-r ay diffraction pattern, which coincide well with the lattice constant α = 6.482 Ǻ of cad mium telluride of the cubic modification. The relative error in ca lc ulating the Miller indices was, respectively, 0.062; 0.077 and 0.093% for the indicated peaks on the roentgenogram.
Intermediate layer Mo -pCdTe . Dichalcogenid have the chemical formula MX2, where M is a transition metal. Bulk dichacogenide is a semiconductor with an indirect band gap, but it turns into a semiconductor with a direct band gap when the crystal thickness decreases to a monolayer. Since monolayers of such materials also efficiently absorb and emit light, they are ideal for creating various since dichalcogenide ditelluride molybdenum MoTe2 (Fig.4)  On. (Fig.4) shows the real structure of the Mo -CdTe boundary. Studies show real structures structure nCdO / pCdTe by X-ray phase analysis, and their structure is based circuit (Fig . 7 .)