TRANSITION IN (001)ALGAAS ALAS/GAAS DOUBLE-BARRIER QUANTUM STRUCTURE FOR INFRARED PHOTODETECTION/

Optical transitions for the (001) Al0.3Ga0.7As/AlAs/GaAs double-barrie r superlattices are evaluated by a semiempirical, tight-binding calcul ation. The oscillator strength between the hole and electron states co nfined in either Gamma- or X-like well are investigated as a function of ALAs slab thickness, Intersub-band transition within the conduction band, including Gamma- and X-like superlattice (SL) states, is descri bed for a quantum well infrared photodetector (QWIP). We found that fo r a specific design structure, it is possible to achieve the dual wave length QWIP with comparable oscillator strength for the 3-5 mu m and 8 -14 mu m atmospheric windows. In addition, by varying the AlAs barrier thickness, the characteristics of bound-to-continuous and bound-to-qu asibound QWIPs are related to the stationary discrete SL states. As th e AlAs thickness increases, the bound-to-continuous state transition b ecomes weak while the bound-to-quasibound state transition becomes mor e significant. Optical coupling between X-like state is relatively wea k and the transition between the different characteristic states is ev en weaker. (C) 1996 American Institute of Physics.