解理面预处理方法对二次外延的影响

Effect of Pretreatment of Cleaved Edges on Overgrowth

利用超晶格解理面方法制备定位生长的InAs量子线.首先以分子束外延技术在GaAs衬底上生长GaAs/AlGaAs超晶格,然后将样品取出外延系统进行解理,对解理面进行预处理之后在(110)解理面上进行二次外延.实验结果显示超晶格解理面的预处理方法对二次外延有重大影响,其中择优腐蚀比自然氧化更有利于量子线的定位生长,过高温度的脱氧除气会导致解理面的GaAs部分出现坑状结构,表明(110)面上的Ga原子容易脱附.同时,Ga原子在(110)面上的迁移长度比较大,原子的择优扩散方向为[00ī]方向.

Site-controlled InAs quantum wires were fabricated with the cleaved edge overgrowth method. First,AIGaAs/GaAs superlattices were grown on GaAs substrate by molecular beam epitaxy. Then, the sample was taken out of the MBE system and cleaved along the [11^-0] direction. After pretreatment, the （110） cleaved edges acted as a nanopattern in overgrowth. Experimental results demonstrate that the pretreatment on the cleaved edge affects the overgrowth and that selective etching is better than natural oxidation for site-controlled growth of quantum wires. High temperature degasification will induce pits on GaAs spacers,indicating that Ga atoms can easily escape from （110） cleaved edges. Furthermore, the surface diffusion length of Ga atoms on the （110） surface is long and the preferred diffusion direction of the atoms on （110） surface is toward [001^-].