摘要
用经验的紧束缚方法对短周期的(Si)_n/(Ge)_m形变超晶格的电子态进行了计算。结果表明,由于布里渊区折迭的要求,只有当n+m=10时超晶格才可能产生直接能隙。对周期为n+m=10的超晶格,Γ,N,△处的导带谷间的相对位置对直接能隙的形成具有决定作用,而n的大小与衬底的组分对此有极大影响。(Si)_6/(Ge)_4和(Si)_8/(Ge)_2超晶格在Si_(1-x)Ge_x衬底上生长时,当0.4≤x≤1.0时形成直接或近直接能隙,而(Si)_4/(Ge)_6超晶格当0.3≤x≤0.6时成为直接能隙,对(Si)_2/(Ge)_8超晶格则不存在直接能隙。
The electronic structures of short period (Si)_n/(Ge)_mStrainedlayer superlattices (SLS's) are calculated using empirical tight-binding method. The results indicate that due to the zone-folding, only the SLS's with n+m=10 have the posibility to form direct band gap. For SLS's with n+m=10, the type of energy gap is determined by the relative energies of conduction band valleys at Γ, N, and Δ. However, the Ge layers number and the composition of substrate play an important role. For (Si)6/(Ge)4 and (Si)8/(Ge)2 SLS's grown on Si(1-x)Ge_x substrate, direct or quasidirect band gap could be got for the substrate composition 0.4≤x≤1.0 For (Si)4/(Ge)6, direct gap could be obtained only for 0. 3≤x≤0.6, and in (Si)2/(Ge)8 SLS's the gap could not be direct for all substrate composition.
出处
《物理学报》
SCIE
EI
CAS
CSCD
北大核心
1993年第8期1317-1323,共7页
Acta Physica Sinica
关键词
超晶格半导体
能带结构
能隙
硅/锗
Band structure
Semiconducting silicon
Semiconductor superlattices
