关于RHEED振荡技术优化GaAs(110)量子阱生长的研究

Optimization of GaAs (110) quantum well material growth technology by reflection high energy electron diffraction

在GaAs(110)衬底上生长的半导体材料有诸多优良性能,使得在非极性GaAs(110)衬底上获得高质量各类异质结材料,成为近年来分子束外延生长关注的课题.考虑GaAs(110)表面是Ga和As共面,最佳生长温度窗口很小;反射式高能电子衍射的(1×1)再构图案对生长温度和V/Ⅲ束流比不敏感,难于通过观察再构图案的变化,准确地找到最佳生长条件.作者在制备GaAs(110)量子阱过程中,观察到反射式高能电子衍射强度振荡呈现出的单双周期变化.这意味着不同工艺条件下,在GaAs(110)衬底上量子阱有单层和双层两种生长模式.透射电子显微镜和室温光致荧光光谱测量结果表明:在双层生长模式下量子阱样品光学性能较差,而在单层生长模式下量子阱光学性能较好,但是界面会变粗糙.利用这一特点,我们采用反射式高能电子衍射强度振荡技术,找到了一种在GaAs(110)衬底上生长高质量量子阱的可行方法.

Recently, there is an increasing interest in the molecular beam epitaxy growth of various high quality heterostructures on the nonpolar GaAs（110） surface for the unique properties which arise from this unconventional orientation. Considering that the Ga and As atoms are coplanar in GaAs（110） surface, the range of best growth temperature is small. It is difficult to find the best growth condition by observing the change of reflection high energy electron diffraction （RHEED） pattern because this kind of （ 1 ×1） RHEED pattern is insensitive to growth temperature and Ⅴ/Ⅲ beam equivalent pressure ratio. In the process of the GaAs （110） quantum well growth, we observed the single and double period variation of oscillation of RHEED intensity： This implies that there are two growth modes （monolayer-by-monolayer and bilayer-by-bilayer） of GaAs quantum wells growing on the GaAs （110） substrate under different growth conditions. The measurements of transmission electron microscopy and photoluminescence at room temperature showed that the quantum wells have very bad optical property under the bilayer-by-bilayer growth mode, while the quantum wells grown under the monolayer-by-monolayer growth mode have much better optical property with rough interfaces. By means of RHEED oscillations, high quality quantum wells have been grown on GaAs （110） substrate under optimized growth conditions.