MgZnO/ZnO异质结构的发光性质研究

Photoluminescence Properties of MgZnO/ZnO Heterostructure Fabricated by P-MBE Method

本文利用等离子体辅助分子束外延(P-MBE)技术在蓝宝石(Al_2O_3)衬底上生长了Mg_(0.12)Zn_(0.88)O(100nm)/ZnO(20nm)/Mg_(0.12)Zn_(0.88)O(40nm)异质结构,测得样品的X射线衍射谱表明,在34.56°的位置出现很强的(002)方向衍射峰,其半高宽度为0.20°,比Mg_(0.12)Zn_(0.88)O合金薄膜的半高宽度0.15°明显展宽。通过光致发光谱研究了MgZnO/ZnO/MgZnO异质结构的光学性质,室温下测得在370nm(3.35eV)位置有很强的紫外发光,而在348nm(3.56eV)的位置处有一个较弱的发光,这两个峰分别被归结于来自ZnO层和MgZnO盖层的发光。室温下的吸收光谱中,在上述两个峰的位置附近分别存在很明显的吸收,指示了带边吸收来自于MgZnO和ZnO两种材料。通过变温发光谱研究了异质结构中载流子弛豫、复合的规律。随着温度增加,来自于ZnO层和MgZnO层的发光强度比增加,这归结为MgZnO/ZnO异质结构存在界面势垒所致。

This paper reported the optical properties of MgZnO ( 100nm)/ZnO (20nm)/MgZnO (40nm) heterostructure on sapphire(001) substrate fabricated by plasma-assisted molecular beam epitaxy (P-MBE). Crystal structure of the sample was investigated by X-ray diffraction spectra. Photoluminescence (PL) spectra at RT exhibit an intense ultraviolet emission from ZnO layer at 370nm (3. 35eV) and a very weak emission peak from MgZnO layer at 348nm (3.56eV). Absorption spectrum of the sample at RT shows two absorption edges corresponding to ZnO and MgZnO layers. PL spectra at different temperature give that the ratio of UV emissions from ZnO and MgZnO layers increases with the temperature rising from 81K to 298K, indicating the existence of an interface potential barrier in MgZnO /ZnO heterostructure.