Temperature dependence of the optical properties in p-Cd 0.96 Zn 0.04 Te single crystals
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T.W. Kim Department of Physics, Kwangwoon University, 447-1 Wolgye-dong, Nowon-ku, Seoul 139-701, Korea (Received 10 February 2001; accepted 29 March 2001)
Photoluminescence (PL) measurements were performed on p-Cd0.96Zn0.04Te single crystals to investigate the dependence of the excitons on temperature. The activation energies and the longitudinal acoustic parameters of the excitons were determined from the temperature dependence of the PL spectra and were in reasonable agreement with the theoretical calculations. These results can help improve understanding for the application of p-CdxZn1−xTe single crystals in optoelectronic devices.
I. INTRODUCTION
II. EXPERIMENTAL DETAILS
Cd x Zn1−xTe semiconductor materials have attracted much attention because of their potential applications in optoelectronic devices, such as infrared photodetectors and optoelectronic modulators, due to their low thermal noise and large absorption coefficients.1–5 In particular, Cd x Zn1−xTe wide-gap semiconductors have been used as substrates for photovoltaic and photoconductive infrared detectors because their lattices are matched with those of Hg1−xCdxTe and Hg1−x ZnxTe narrow-gap semiconductors.6,7 Even though some preliminary works have investigated the optical properties in p-Cd x Zn1−xTe single crystals,8 –10 detailed studies of the temperature dependence of the excitons in the samples have yet to be conducted. Furthermore, an understanding of the temperature dependence of the exciton behaviors is very important for determining the optical properties and is necessary for the fabrication of high-efficiency optoelectronic devices.11,12 This paper reports photoluminescence (PL) measurements which were performed to investigate the temperature dependence of the excitons in the p-Cd 0.96 Zn 0.04Te. The line width behavior of the excitons is described, and the activation energies and the coupling constants of the excitons are determined from the temperaturedependent PL spectra.
The samples used in this study were nominally undoped p-Cd 0.96 Zn 0.04 Te grown by using an improved Bridgemann method. The carrier concentration, the mobility, and the resistivity of p-Cd 0.96 Zn 0.04 Te at room temperature were approximately 1015 cm−3 100 cm2/ (Vs), and 105 ⍀ cm, respectively. The PL measurements were done using a 75-cm monochromator with an RCA 31034 photomultiplier tube. The excitation source was the 5145-Å line of an Ar-ion laser, and the power was 100 mW. The sample was mounted on a sample holder, and the sample temperature was controlled between 10 and 300 K by using a He displex system.
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J. Mater. Res., Vol. 16, No. 8, Aug 2001 Downloaded: 19 Apr 2015
III. RESULTS AND DISCUSSION
The results for the temperature dependence of the PL spectra of p-Cd 0.96 Zn 0.04 Te are shown Fig. 1. The PL spectrum obtained at 11 K is shown in the top curve of Fig. 1. The peaks at 1.607 and 1.593 eV are considered to be from excitons boun
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