Optimization of the Growth Conditions for Molecular Beam Epitaxy of MgxZn1-xO ($0\leq x\leq 0.12$) Films on Zn-Polar ZnO Substrates

• Published in: Jpn J Appl Phys 2010-07, Vol.49 (7), p.071104-071104-5
• Main Authors: Yuji, Hiroyuki, Nakahara, Ken, Tamura, Kentaro, Akasaka, Shunsuke, Nishimoto, Yoshio, Takamizu, Daiju, Onuma, Takeyoshi, Chichibu, Shigefusa F, Tsukazaki, Atsushi, Ohtomo, Akira, Kawasaki, Masashi
• Format: Article
• Language: eng ; jpn
• ISSN: 0021-4922; 1347-4065
• DOI: 10.1143/JJAP.49.071104

We report on optimization of the growth conditions for Mg x Zn 1-x O ($x=0,0.04,0.05,0.12$) thin films grown on $c$-plane Zn-polar ZnO single crystal substrates by using plasma-assisted molecular beam epitaxy (PAMBE). A normal vector to the ZnO substrate surfaces was angled at $0.5\pm 0.1$\mbox{ \circ } off from the [0001] $c$-axis toward the [$1\bar{1}00$] direction, leading to a stable step-and-terrace structure. A growth temperature ($T_{\text{g}}$) higher than 800 \mbox{ \circ C} led to the ZnO films presenting the first excited state luminescence of A-free excitons in photoluminescence (PL) spectra at 12 K. A $T_{\text{g}}$ higher than 800 \mbox{ \circ C} enhanced optical attributes of a Mg x Zn 1-x O film. The longest PL lifetime of fast-decay components reached 3.5 ns in time-resolved PL measurement for an Mg 0.12 Zn 0.88 O film grown at 900 \mbox{ \circ C}, indicating a concentration of nonradiative recombination centers is substantially eliminated compared to the previously reported PL lifetime of 60 ps for an Mg 0.11 Zn 0.89 O film grown by pulsed laser deposition.