High quality p-type ZnO film grown on ZnO substrate by nitrogen and tellurium co-doping
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1201-H05-25
High quality p-type ZnO film grown on ZnO substrate by nitrogen and tellurium codoping S. H. Park1,2, T. Minegishi1, J. S. Park1, H. J. Lee1,T. Taish3, I. Yonenaga3, D. C. Oh4, M. N. Jung5, J. H. Chang5, S. K. Hong6, and T. Yao1 1
Center for Interdisciplinary Research, Tohoku University, Sendai, 980-8578, Japan National Institute for Materials Science, Tsukuba, 305-0044, Japan 3 Institute for Material Research, Tohoku University, Sendai, 980-8577, Japan 4 Department of Defense Science and Technology, Hoseo University, 336-795, Korea 5 Major of Semiconductor Physics, Korea Maritime University, Pusan 606-791, Korea 6 Nano Information Systems Engineering, Chungnam National Univ., Daejeon, 305-764, Korea 2
ABSTRACT Nitrogen and tellurium co-doped ZnO (ZnO:[N+Te]) films have been grown on (0001) ZnO substrate by plasma-assisted molecular beam epitaxy. The electron concentration of tellurium doped ZnO (ZnO:Te) gradually increases, compared with that of undoped ZnO (u-ZnO). On the other hand, conductivity of ZnO:[N+Te] changes from n-type to p-type characteristic with a hole concentration of 4×1016 cm-3. However, nitrogen doped ZnO film (ZnO:N) still remains as n-type conductivity with an electron concentration of 2.5×1017 cm-3. Secondary ion mass spectroscopy reveals that nitrogen concentration ([N]) of ZnO:[N+Te] film (2×1021 cm-3) is relatively higher than that of ZnO:N film (3×1020 cm-3). 10 K photoluminescence spectra show that considerable improvement of emission properties of ZnO:[N+Te] with an emergence of narrow acceptor bound exciton (AoX, 3.359 eV) and donor-acceptor pair (DAP, 3.217 eV), compared with those of u-ZnO. Consequently, high quality p-type ZnO with high N concentration is realized by using Te and N co-doping technique due to reduction of Madelung energy. INTRODUCTION ZnO has a direct band gap of 3.37 eV at room-temperature and has also attracted attention as a useful material for UV optoelectronic applications. The large excitonic binding energy of 60 meV also raises the interesting possibility of utilizing excitonic effects in room-temperature devices [1]. In order to realize ZnO-based semiconductor devices, it is indispensable to fabricate ZnO films with p-type as well as n-type conductivity by controllable extrinsic doping. However, ZnO have naturally only n-type conductivity due to the presence of native defects such as oxygen vacancy and zinc interstitial, which hampers obtaining high-quality p-type ZnO layers required for optoelectronic devices. Although there are many reports on p-type nitrogen doped ZnO film by various growth method, high quality p-type ZnO films have not been achieved in terms of poor electrical and optical properties [2-4]. This classical problem is originated from the low solubility limit of ZnO.
In order to solve solubility limit of ZnO, Yamamoto et al. has proposed firstly the alternative co-doping method (N+III-element) based on initio electronic band structure calculations [5]. They have reported that co-doping using reactive III-element enhances the i
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