Properties of p-Type ZnO Grown by Oxidation of Zn-Group-V Compounds
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0957-K08-04
Properties of p-Type ZnO Grown by Oxidation of Zn-Group-V Compounds Eliana Kaminska1, Ewa Przezdziecka2, Anna Piotrowska1, Jacek Kossut3, Piotr Boguslawski2, Iwona Pasternak1, Rafal Jakiela2, and Elzbieta Dynowska2 1 Semiconductor Processing for Photonics, Institute of Electron Technology, Al. Lotnikow 32/46, Warsaw, 02-668, Poland 2 Institute of Physics, PAS, Al. Lotnikow 32/46, Warsaw, 02-668, Poland 3 Institute of Physics, PAS, and ERATO Semiconductor Spintronics, Al. Lotnikow 32/46, Warsaw, 02-668, Poland
ABSTRACT ZnO:N and ZnO:Sb layers were obtained by thermal oxidation of Zn compounds with group-V elements. The films are polycrystalline, with the acceptor concentration in the range 1020 cm-3, and the background concentration of H of 5x1019 cm-3. Transport measurements reveal the p-type conductivity with the hole concentrations exceeding 1017 cm-3. Rich photoluminescence spectra involve excitons bound to neutral acceptors and donor-to-acceptor transitions. p-ZnO:N and p-ZnO:Sb films show transparency of about 85 % in the visible wavelength range, making these materials very promising for transparent electronics. INTRODUCTION In recent years ZnO has emerged as a subject of considerable experimental and theoretical research owing to possible applications for manufacturing of fully functional electronic devices. However, intrinsic doping limitations of ZnO make it difficult to obtain p-type conductivity in this material. On the other hand, for purposes of optically transparent electronics it is vital that ZnO with high hole concentrations is produced in a controllable fashion. Obvious group-I candidates for acceptors, such as Li, turned out to be non-efficient [1]. A considerable attention was devoted to nitrogen, the only group-V dopant with the atomic radius matching that of O, but both hole concentrations and stability of doping are not satisfactory at present. Since straightforward doping approaches seem to be not productive in this respect, various strategies to overcome the difficulties were suggested in the literature [2-5]. In search for appropriate p-type doping procedure, large-size-mismatched As and Sb acceptors [4] have recently received much attention. In this paper we discuss preparation of ptype ZnO by oxidation of Zn-group-V compounds. We extend our recently developed method of obtaining p-ZnO by oxidation of zinc nitride [6] or N-doped ZnTe [7] to other Zn compounds. In particular, oxidation of Zn-Sb source material reproducibly leads to p-ZnO layers with the hole concentration exceeding 1x1017 cm-3 and excellent optical properties. Herein, we compare the electrical, structural, and optical properties of N- and Sb-doped p-type ZnO. Since oxidation implies oxygen-rich conditions, we avoid the problem of compensation by oxygen vacancies acting as donors [4].
EXPERIMENTAL Zn-V source materials were synthesized in a magnetron multi-target sputtering system on unheated (0001)-oriented sapphire substrates. The base pressure in the vacuum chamber was ~1x10-7mbar. The working pressure was
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