Radiative recombination of electron-hole pairs spatially separated due to quantum-confined Stark and Franz-Keldish effects in ZnO/Mg0.27Zn0.73O quantum wells

被引:102
作者
Makino, T [1 ]
Tamura, K
Chia, CH
Segawa, Y
Kawasaki, M
Ohtomo, A
Koinuma, H
机构
[1] RIKEN, Inst Phys & Chem Res, Photodynam Res Ctr, Sendai, Miyagi 9800845, Japan
[2] Tohoku Univ, Inst Mat Res, Sendai, Miyagi 9808577, Japan
[3] Tokyo Inst Technol, Mat & Struct Lab, Yokohama, Kanagawa 2268503, Japan
[4] Tokyo Inst Technol, Dept Innovat & Engn Mat, Yokohama, Kanagawa 2268503, Japan
[5] Tohoku Univ, Dept Phys, Sendai, Miyagi 9808577, Japan
[6] Combinatorial Mat Explorat & Technol, Tsukuba, Ibaraki 3050044, Japan
关键词
D O I
10.1063/1.1507606
中图分类号
O59 [应用物理学];
学科分类号
摘要
We studied photoluminescence (PL) properties of eighteen samples of wurtzite ZnO/MgxZn1-xO multiple quantum wells (x=0.12 and 0.27) with various well widths (L-w) of 0.7-4.65 nm. Radiative recombination of the electron-hole pairs that are spatially separated due to the quantum-confined Stark (QCS) and Franz-Keldish (QCFK) effects was observed in two thicker samples at 5 K. This PL band is located approximate to 40 meV in energy below the emission band of the localized excitons and approximate to 60 meV below the absorption energy of the free exciton transition. One can not observe such kind of luminescence unless both of the following conditions are accomplished: (1) higher Mg concentration (x=0.27) and (2) L(w)greater than or equal to4.23 nm. These experimental findings do not contradict the following two characteristic features for the QCS and QCFK effects; the magnitude of the electric field due to spontaneous and piezoelectric polarizations and the depth of the triangle-shaped potential wells are the monotonically increasing functions of Mg concentration and the L-w, respectively. The coupling strength with longitudinal-optical phonons, which is determined from the relative luminescence intensities of the phonon replicas, is significantly larger than that between the localized excitons and phonons. It is considered that the strong electric field increases the distance between electron and hole charge distributions from that determined by the Coulomb force and leads to the enhancement in the phonon interaction. (C) 2002 American Institute of Physics.
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页码:2355 / 2357
页数:3
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