The electronic structure and optical properties of III-V and II-VI semiconductor superlattices are treated theoretically using a superlattice-representation formalism. The band structure is obtained from superlattice Kp theory. The theory is based on closed analytic calculations of the superlattice states at wave vector K=0 and the envelope-function approach. The known parameters of the bulk constituents represent the only input. The electron effective masses and gaps of GaAs/Ga1-xAlxAs (type I), InAs/GaSb (type II), and HgTe/CdTe (type III) are investigated for a wide range of layer widths using the recently deduced large valence-band offset of HgTe/CdTe. The behavior of the masses is also discussed in terms of the f-sum rule. The calculated fundamental absorption coefficients for InAs/GaSb and HgTe/CdTe are in excellent agreement with experimental data. The intersubband absorption between the lowest two superlattice conduction bands is investigated. In the thick-barrier limit of GaAs/Ga1-xAlxAs the absorption can be larger than the fundamental absorption and as narrow as a laser linewidth. In the thin-barrier limit the absorption is smaller and broader, as illustrated for InxGa1-xAs/InyAl1-yAs.
ASJC Scopus subject areas
- Condensed Matter Physics