Intracenter excited state of copper in Cu-compensated InP
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TRONIC AND OPTICAL PROPERTIES OF SEMICONDUCTORS
Intracenter Excited State of Copper in Cu-Compensated InP V. A. Melnika^, N. N. Pribylovb, S. I. Rembezaa, and Ph. V. Makarenkoa aVoronezh
State Technical University, Moskovskii pr. 14, Voronezh, 394026 Russia ^e-mail: [email protected] bRussian State Open Technical University of Communication Lines, Voronezh Branch, ul. Uritskogo 75A, 394026 Russia Submitted April 1, 2008; accepted for publication April 9, 2008
Abstract—In studies of the spectra of the photoconductivity of impurity of the samples of Cu-compensated InP, a resonant transition from one state of copper to another with the maximum of optical energy of excitation of 0.31 eV is found. The temperature dependence of the intensity’s maximum of the intracenter transition in the range from 90 to 450 K is obtained. It is established that the thermal energy of excitation is 0.42 eV. PACS numbers: 71.55.Eq, 78.30.Fs, 78.40.Fy, 72.40.+w DOI: 10.1134/S1063782609030026
1. INTRODUCTION After compensation by copper, InP and GaP manifest a high sensitivity to radiation. The reasons causing the photosensitivity are not still understood completely. According to the data [1], copper in GaP:Cu and InP:Cu forms two levels distanced by 0.2 eV. The lower of the levels, the level A, is located above the valence band’s top by ~0.5 eV for GaP:Cu and by ~0.3 eV for InP:Cu. The density of states of the upper level B is much lower than that of the lower level in this case. It was shown [2] that Cu exhibits amphoteric properties and, supposedly, its atom can be in two states, namely, a substitution state with a tetrahedral configuration of bonds and associated with a vacancy in the interstitial state. Due to this, the centers that exhibit both acceptor (A–) and donor (B+) properties can emerge in GaP:Cu. In [3], the photoconduction band that peaked at 1.05 eV was associated with the intracenter excitation of the Cu center. To interpret the features of the spectra of the intrinsic photoconductivity of InP:Cu, authors of [4] accepted the notions previously formulated for the Cu centers in GaP. However, to our knowledge, there are no direct experimental data indicating the presence of the bands of intracenter excitation of Cu in InP. Assuming that Cu in this semiconductor material manifests similar properties, we started the goal of studying the photoconductivity of impurity in the InP:Cu samples. 2. EXPERIMENTAL AND RESULTS The InP samples used by us were fabricated similarly to those presented in [4]. The contacts to them, which were shaped as parallel strips, were fabricated via soldering the copper wires with a tin–silver solder (96.5% of Sn and 3.5% of Ag) at a distance of 2.5–3 mm.
The experiments were performed with the use of a setup on the basis of an IKS-21 infrared spectrometer with a NaCl prism modernized for control and data acquisition from the computer at a constant radiation flux incident onto the sample [5, 6]. The photoconductivity’s signal was taken from the load resistor with a resistance of 100 kΩ and detected by th
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