Abstract
Absorption spectra which originate from directvalence-band-to-conduction-band transitions in strained-layersuperlattices (SLSs) are studied theoretically. The electronicstructures are calculated by using the Luttinger-Kohn Hamiltonian inthe Kronig-Penney model. The absorption coefficients are evaluated bytaking the mixing of heavy- and light-hole states into account. As aresult of calculation, firstly, origins of fine structures in theabsorption spectra observed at a room temperature for type IZnSe(22, Å)--ZnS(23, Å) SLS are clarifiedsatisfactorily. Secondly, novel properties of type II ZnTe--ZnSe arepredicted, i.e. it is revealed that the absorption intensity is oneorder of magnitude less in type II SLS than in type I SLS, and that intype II SLS the strength for any transitions to the higher conductionand from the higher valence subbands is greatly enhanced, in sharpcontrast to the type I SLS.
