• Nishimoto, Yoshio
• Takamizu, Daiju
• Onuma, Takeyoshi
• Chichibu, Shigefusa F.
• Yuji, Hiroyuki
• Nakahara, Ken
• Akasaka, Shunsuke
• Ohtomo, Akira
• Tamura, Kentaro
• Tsukazaki, Atsushi

Abstract

<jats:p>We report on optimization of the growth conditions for Mg<jats:sub><jats:italic>x</jats:italic></jats:sub>Zn<jats:sub>1-<jats:italic>x</jats:italic></jats:sub>O (<jats:italic>x</jats:italic>=0,0.04,0.05,0.12) thin films grown on<jats:italic>c</jats:italic>-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±0.1° off from the [0001]<jats:italic>c</jats:italic>-axis toward the [1100] direction, leading to a stable step-and-terrace structure. A growth temperature (<jats:italic>T</jats:italic><jats:sub>g</jats:sub>) higher than 800 °C led to the ZnO films presenting the first excited state luminescence of A-free excitons in photoluminescence (PL) spectra at 12 K. A<jats:italic>T</jats:italic><jats:sub>g</jats:sub>higher than 800 °C enhanced optical attributes of a Mg<jats:sub><jats:italic>x</jats:italic></jats:sub>Zn<jats:sub>1-<jats:italic>x</jats:italic></jats:sub>O film. The longest PL lifetime of fast-decay components reached 3.5 ns in time-resolved PL measurement for an Mg<jats:sub>0.12</jats:sub>Zn<jats:sub>0.88</jats:sub>O film grown at 900 °C, indicating a concentration of nonradiative recombination centers is substantially eliminated compared to the previously reported PL lifetime of 60 ps for an Mg<jats:sub>0.11</jats:sub>Zn<jats:sub>0.89</jats:sub>O film grown by pulsed laser deposition.</jats:p>

Topics

• impedance spectroscopy
• surface
• photoluminescence
• single crystal
• thin film
• pulsed laser deposition