Electronic and optical properties of III-V and II-VI semiconductor superlattices

Abstract

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 K\ensuremath{\cdot}p 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/${\mathrm{Ga}}_{1\mathrm{\ensuremath{-}}\mathrm{x}}$${\mathrm{Al}}_{\mathrm{x}}$As (type I), InAs/GaSb (type II), and HgTe/CdTe (type III) are investigated for a wide range of layer widths using the recently deduced large valence-band offset of HgTe/CdTe. The behavior of the masses is also discussed in terms of the f-sum rule. The calculated fundamental absorption coefficients for InAs/GaSb and HgTe/CdTe are in excellent agreement with experimental data. The intersubband absorption between the lowest two superlattice conduction bands is investigated. In the thick-barrier limit of GaAs/${\mathrm{Ga}}_{1\mathrm{\ensuremath{-}}\mathrm{x}}$${\mathrm{Al}}_{\mathrm{x}}$As 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 ${\mathrm{In}}_{\mathrm{x}}$${\mathrm{Ga}}_{1\mathrm{\ensuremath{-}}\mathrm{x}}$As/${\mathrm{In}}_{\mathrm{y}}$${\mathrm{Al}}_{1\mathrm{\ensuremath{-}}\mathrm{y}}$As.