摘要
按照Peressi等的第一性原理赝势计算得到的原子几何构形及能带边不连续值,采用紧束缚方法计算了生长在Si(001)衬底上的超晶格(Si_2)_4/(GaAs)_4的电子能带结构及光跃迁振子强度.相应于两种不同的原子几何构形:X端界面及Y端界面情况,超晶格具有不同的基本带隙.但是不管哪种情况,它们都存在能量近乎简并的两类导带底能谷——Γ能谷及△能谷,它们的价带顶都处在Γ点.X端界面超晶格的价带顶附近的状态主要由GaAs 层的价态波函数组成.对于Y端界面超晶格的价带顶附近的状态,Si层和GaAs层的价态波函数有较大的混和.两类超晶格的导带Γ能谷的状态主要由Si层的原来体导带X能谷经布里渊区折叠而组成.价带顶和导带底附近的带间跃迁振子强度大部分都近乎为零;价带顶附近能级至价带顶能级间的光跃迁沿[001]方向的振子强度有较大的值;导带底至导带底附近能级的光跃迁,只有Y端界面超晶格具有比较大的振子强度.
With using the atomic geometrical structures and band-offset extracted from the results of computations by Peressi et al with first principle pseudopotential method, the electronic band structures and the optical oscillator strengths for the superlatti-ces (Si2)4/(GaAs)4 grown on the Si(00l) substrates were calculated in tight-binding frame. The fundamental gap of superlattices is different for two geometrical structures: X-termination interface and Y-termination interface. And there are two conduction band energy valleys—Γ valley and A valley, which are almost degenerative, and a valence band energy valley on Γpoint for both X-termination and Y-termination superlattices. The states near the valence band top mainly originate from the valence states of GaAs layers for X-termination superlattice and are constituted by mixture of the valence states of Si and GaAs layers for Y-termination superlattice. The conduction band states near the Γ valley mainly originate from the X valley of bulk Si conduction band which is formed from Brillouin zone folding in superlattices. Most optical oscillator strengths for the transitions between valence band and conduction band are nearly equal to zero. The optical oscllator srengths for the transitons from the lower valence band levels to the valence band top level with [001] polarity have larger values for both two termination superlattices. Those for the transition from the conduction band bottom level to the higher levels have substantial values only for the Y-termination superlattice.
出处
《物理学报》
SCIE
EI
CAS
CSCD
北大核心
1995年第12期1984-1993,共10页
Acta Physica Sinica
基金
国家自然科学基金资助的课题.