Give some Examples of direct and indirect band gap semiconductors?
direct band gap-semiconductor in which the bottom of the
conduction band and the top of the valence band occur at the
momentum k=0;in the case of d.b.s. energy released during
band-to-band electron recombination with a hole is converted
primarily into radiation (radiant recombination); wavelength of
emitted radiation is determined by the energy gap of semiconductor;
examples of d.b.s. GaAs, InP, ZnS, ZnSs, CdS, CdSe etc.
indirect bandgap semiconductor --semiconductor in which bottom
of the conduction band does not occur at effective momentum k=0,
i.e. is shifted with respect to the top of the valence band which
occurs at k=0; energy released during electron recombination with a
hole is converted primarily into phonon; e.g. Si, Ge, GaP, GaAsp
,Ge etc, .