title: Enhanced Light Emission due to Formation of Semi-polar InGaN/GaN Multi-quantum Wells.
abstract: InGaN/GaN multi-quantum wells (MQWs) are grown on (0001) sapphire substrates by metal organic chemical vapor deposition (MOCVD) with special growth parameters to form V-shaped pits simultaneously. Measurements by atomic force microscopy (AFM) and transmission electron microscopy (TEM) demonstrate the formation of MQWs on both (0001) and ([Formula: see text]) side surface of the V-shaped pits. The latter is known to be a semi-polar surface. Optical characterizations together with theoretical calculation enable us to identify the optical transitions from these MQWs. The layer thickness on ([Formula: see text]) surface is smaller than that on (0001) surface, and the energy level in the ([Formula: see text]) semi-polar quantum well (QW) is higher than in the (0001) QW. As the sample temperature is increased from 15 K, the integrated cathodoluminescence (CL) intensity of (0001) MQWs increases first and then decreases while that of the ([Formula: see text]) MQWs decreases monotonically. The integrated photoluminescence (PL) intensity of (0001) MQWs increases significantly from 15 to 70 K. These results are explained by carrier injection from ([Formula: see text]) to (0001) MQWs due to thermal excitation. It is therefore concluded that the emission efficiency of (0001) MQWs at high temperatures can be greatly improved due to the formation of semi-polar MQWs.
authors.affiliation: Department of Electronic Engineering, Xiamen University, Xiamen, 361005, People's Republic of China.
authors.forename: Wan-Ru
authors.initials: WR
authors.lastname: Zhao
authors.affiliation: Department of Physics, Xiamen University, Xiamen, 361005, People's Republic of China.
authors.forename: Guo-En
authors.initials: GE
authors.lastname: Weng
authors.affiliation: School of Electronic Science and Engineering, Nanjing University, Nanjing, 210093, People's Republic of China.
authors.forename: Jian-Yu
authors.initials: JY
authors.lastname: Wang
authors.affiliation: Department of Electronic Engineering, Xiamen University, Xiamen, 361005, People's Republic of China.
authors.forename: Jiang-Yong
authors.initials: JY
authors.lastname: Zhang
authors.affiliation: School of Physics and Optoelectronic Engineering, Dalian University of Technology, Dalian, 116024, People's Republic of China. hwliang@dlut.edu.cn.
authors.forename: Hong-Wei
authors.initials: HW
authors.lastname: Liang
authors.affiliation: World Premier International (WPI) Center for Materials Nanoarchitectonics (MANA), National Institute for Materials Science (NIMS), Namiki 1-1, Tsukuba, Ibaraki, 305-0044, Japan.
authors.forename: Takashi
authors.initials: T
authors.lastname: Sekiguchi
authors.affiliation: Department of Electronic Engineering, Xiamen University, Xiamen, 361005, People's Republic of China. bzhang@xmu.edu.cn.
authors.forename: Bao-Ping
authors.initials: BP
authors.lastname: Zhang
keywords: Cathodoluminescence; InGaN/GaN multi-quantum wells; Photoluminescence; Semi-polar