Donor Complexes Formed by Cu and Zn Multi-Acceptor Impurities in Ge Crystals
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HYSICAL PROPERTIES OF CRYSTALS
Donor Complexes Formed by Cu and Zn Multi-Acceptor Impurities in Ge Crystals Z. A. Aghamalieva,b,* and G. Kh. Azhdarova a Institute
of Physics, National Academy of Sciences of Azerbaijan, Baku, AZ1143 Azerbaijan b Baku State University, Baku, AZ1147 Azerbaijan *e-mail: [email protected] Received February 24, 2020; revised February 24, 2020; accepted June 1, 2020
Abstract―Based on Hall effect measurements it is shown that quenching of complexly doped GeZn,Сu crystals at 1070–1100 K leads to the formation of additional electrically active donor centers with activation energy Еd = Еc – 93 meV in them. Further annealing of crystals at 550–570 K leads to disappearance of these centers. The most likely model of additional deep donor centers is a complex consisting of a pair of substituent zinc atoms (Zns) and interstitial copper atoms (Cui). The necessity of taking into account the formation of additional donor centers in precise doping GeZn crystals with copper by the method of decomposition of supersaturated solution of impurity in matrix is demonstrated. DOI: 10.1134/S1063774520060036
INTRODUCTION Copper and zinc in germanium crystals belong to multiplet deep acceptor centers; they significantly affect the electrical properties of the matrix in a wide temperature range. Three acceptor levels of copper with energies Еv + 40 meV, Еv + 0.330 meV, and Еc – 260 meV and two acceptor levels of zinc with energies Еv + 30 meV and Еv + 90 meV are attributed to substituent atoms of these impurities (Cus, Zns) in germanium crystals [1]. Copper, in contrast to zinc, rapidly diffuses in germanium. For this reason, the decomposition of its supersaturated solution in a matrix at thermal treatment is often used for precise control of impurity concentration in crystal. However, the tendency of rapidly diffusing impurities to interaction with different lattice defects upon thermal treatment of semiconductor may lead to the formation of new electrically active complexes, significantly affecting the electronic properties of material. It was found in [2–4] that additional electrically active centers arise in Ge crystals and solid Ge–Si solutions after their doping with copper and one of the acceptor impurities of group III (Al, Ga, In) with a low activation energy and treating in a certain temperature range. These centers were attributed to the complexes formed in the matrix as a result of coupling of substituent acceptor-impurity atoms with rapidly diffusing copper atoms. Note that a similar coupling of acceptor impurities of III-group elements and rapidly diffusing Mg impurity, leading to the formation of electrically active centers in the matrix, occurs also in Si, as was shown recently in [5].
In this work, we investigated the influence of treatment in the range of 1000–1150 K on the spectrum of impurity states in GeZn,Сu crystals based on Hall effect measurements. The purpose was to establish the possibility and conditions for the formation of additional electrically active centers in Ge cryst
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