OPTIMIZED SIGE SI MULTIPLE-QUANTUM WELLS FOR DETECTOR APPLICATIONS/

We present p-type SiGe/Si heterostructures optimized for performance a t approximate to 10 mu m. Full scale semi-empirical pseudo-potential c alculations were used to obtain the miniband structure and optical mat rix elements for these systems. The effect of the space charge potenti al due to the doping distribution in the whole of the device structure is taken into account and its effect upon the structural parameters d etermining the key electronic transitions evaluated. This investigatio n also addresses a vital device design question about the maximum perm itted doping revels at which the optical response is still dominated b y transitions originating in the wells. Although high doping levels ar e desirable to increase the signal, the build up of space charge poten tial eventually destroys the functionality of the wells. The resulting modification of the polarization dependence and spectral shape are pr esented as a function of the strength of the space charge potential. A detailed quantitative description of these relationships is given whi ch may serve as a useful guide for design of optical devices.