Smart Heterostructures Based on Solid Solution ZnCdHgTe
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Smart Heterostructures Based on Solid Solution ZnCdHgTe. Galina M. Khlyap and Petro G. Sydorchuk State Pedagogical University, 24 Franko str., Drohobych, 82100, Ukraine Jacek Polit1 and Macej Oszwaldowsky2 1 Institute of Physics, University of Rzeszow, 35-310 Rzeszow, Rejtana 16A, Poland 2 Institute of Physics, Politechnika Poznanska, Piotrowo 3, 60-965, Poznan, Poland ABSTRACT Current – voltage (IVC) and capacitance – voltage (CVC) of heterostructures (Cd, Zn)Te/ZnCdHgTe are studied for the first time. Thin films ZnxCdyHg1-x-yTe were grown on monocrystalline (111) CdTe and ZnTe substrates by PLE technology. Deposition was carried out on substrates held at temperatures near 290 K. The thickness of investigated films was estimated to be about 5 µm. Electric characteristics of the as-grown structures were examined under T = 77 – 290 K in the wide range of applied bias. All investigated samples have demonstrated diode-like IVC and CVC under test signal frequency f = 1 kHz. Heterostructures CdTe/ZnCdHgTe have exhibited a room temperature photosensitivity in spectral range 0.50 – 0.65 µm. . INTRODUCTION Smart narrow-gap semiconductor materials belonging to the group A2B6 compounds are seemed to be of particular interest for design of optoelectronics devices used for various needs of navigation. The heterojunctions based on epitaxial layers ZnCdHgTe and wide gap monocrystals Cd(Zn)Te are seemed to be of essential importance owing to simplicity and reliability of growth technology (modified liquid-phase epitaxy or pulse laser evaporation technique. The investigation of experimental data obtained from simplest electric-field measurements provides a reasonable base for computational modeling of the graded-gap heterostructures. Quaternary solid solutions ZnxCdyHg1-x-yTe intensively investigated during the last years [1,2] are usually grown by the liquid-phase epitaxy method [3]. Epilayers with compositions x and y not exceeding 0.2 are of particular interest for different optoelectronic applications because this material appears as an alternative to the well-known ternary solid solutions CdyHg1-yTe and ZnxHg1-xTe [3 and references therein]. EXPERIMENAL DETAILS (100)-oriented monocrystalline ZnTe and CdTe wafers were selected as substrates. ZnCdHgTe films were grown by pulse laser deposition (PLD) technique under dynamic vacuum mode. Parameters of the laser used are listed in Table 1.
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Table 1. Parameters of Nd:YAG laser used for growth of investigated heterostructures. Laser
Wavelength, µm
Pulse duration, µs
Repetition rate, Hz
Pulse peak power, J
Nd:YAG
1.06
150
10
0.6
The growth chamber has provided vacuum level no more than 10-5 Torr. The pellets obtained from powdered mixtures of binary compounds CdTe, ZnTe, HgTe under pressure of 150 technical atmospheres were used as the source for layer deposition. Samples of the as-grown structures with layers of 5.22 µm thickness and 0.3 – 0.5 cm2 electrical area were chosen for measurements. All electric studies were performed under the room temperatur
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