Effect of Hydrogen Treatment on Room -Temperature Electric-Field Induced Properties in Narrow-Gap ZnCdHgTe Thin Films
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Effect of Hydrogen Treatment on Room -Temperature Electric-Field Induced Properties in Narrow-Gap ZnCdHgTe Thin Films Galina M. Khlyap and Petro G. Sydorchuk State Pedagogical University, 24 Franko str., Drohobych, 82100, Ukraine Jacek Polit1 1 Institute of Physics, University of Rzeszow, 35-310 Rzeszow, Rejtana 16A, Poland ABSTRACT The effect of hydrogen treatment on room temperature electric properties of narrow-gap semiconductor thin films ZnxCdyHg1-z-yTe (0 < x < 0.50, 0.20 < y < 0.40) is investigated for the first time. ZnCdHgTe films of 2 – 5 µm thickness were grown on glass substrates by pulsed laser deposition technique. As-grown films were thermally treated in the flow of molecular H2 at 2000C during 24 hours. Comparison between electric characteristics measured before and after hydrogenation showed sufficient changes of the film resistance and appearance of photosensitivity in the visible wavelength range. Study of current-voltage characteristics of the films revealed appearance and significant change of diode-like properties. INTRODUCTION The narrow-gap semiconductor solid solution ZnCdHgTe has been investigated for decades as an alternative material to well-known HgCdTe [1 and references therein]. Requirements of the large area thin film-based optoelectronics force one to make efforts for simple and reliable obtaining active elements with in-advance determined properties. Pulsed laser deposition (PLD) technique is seemed to be one of the requested methods. Recently [1] we have reported electric characteristics of heterostructures based on PLD-grown ZnxCdyHg1-x-yTe (0 < x < 0.5, 0 < y < 0.5) films. The main problem of practical applicability of as-grown films is how to make them photosensitive. The samples subjected to the study were of p-type conductivity. Annealing in mercury atmosphere inversed the conductivity type, but caused no registerable photosensitivity. So, the aim of the experiments presented in the paper is to show the possibility of inducing photosensitivity by means of heating samples in the flow of molecular hydrogen. In spite of numerous publications considering effect of H2 plasma on different properties of the semiconductor materials [2-4] there are no references concerning the influence of molecular hydrogen flow on the properties of A2B6 compounds (bulk as well as films). EXPERIMENTAL DETAILS As it was described previously [1], ZnCdHgTe films were grown by means of PLD using laser parameters listed in the Table 1. Table 1. Parameters of Nd:YAG laser used for growth of investigated heterostructures. Laser
Wavelength, µm
Pulse duration, µs
Repetition rate, Hz
Nd:YAG
1.06
150
10
Pulse peak power, J 0.6
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X-ray diffraction studies of the as-grown samples (Fig.1) have shown the single crystal structure of the layers. Microstructure analysis revealed the following composition of the films: x = 0.08, y = 0.37 (further the samples will be referred as Set 1) and x = 0.48, y = 0.22 (further referred as Set 2). Room temperature electric measurements and estimations of int
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