Characterization of N-doped ZnO layers grown on (0 0 0 1) GaN/Al2O3 substrates by molecular beam epitaxy |
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| Authors: | D C Oh A Setiawan J J Kim H J Ko H Makino T Hanada M W Cho T Yao |
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| Institution: | a Institute for Materials Research, Tohoku University, Katahira 2-1-1, Aoba-ku, Sendai 980-8577, Japan;b Center for Interdisciplinary Research, Tohoku University, Aramakiazaaoba, Aoba-ku, Sendai 980-8578, Japan;c Division of Technology, Korea Photonics Technology Institute, Bonchon-dong 459-3, Book-koo, Kwangjoo 500-210, South Korea |
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| Abstract: | We investigated the optical properties and electrical properties of N-doped ZnO layers grown on (0 0 0 1) GaN/Al2O3 substrates by molecular beam epitaxy, employing 10 K photoluminescence (PL) measurements, current–voltage (IV) measurements, capacitance–voltage (CV) measurements, and 100 K photocapacitance (PHCAP) measurements. 10 K PL spectra showed that excitonic emission is dominant in N-doped ZnO layers grown after O-plasma exposure, while overall PL emission intensity is significantly reduced and deep level emission at around 2.0 2.2 eV is dominant in N-doped ZnO layers grown after Zn exposure. IV and CV measurements showed that N-doped ZnO layers grown after Zn exposure have better Schottky diode characteristics than O-plasma exposed samples, and an N-doped ZnO layer grown at 300 °C after Zn exposure has best Schottky diode characteristics. This phenomenon is presumably due to lowered background electron concentration induced by the incorporation of N. PHCAP measurements for the N-doped ZnO layer revealed several midgap trap centers at 1.2 1.8 eV below conduction band minimum. |
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| Keywords: | ZnO Schottky contact Deep level |
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