A complete and self-consistent model for the evaluation of spontaneous
emission in microcavity semiconductor post lasers is presented. It ta
kes into account the continuous electromagnetic field spectrum of the
resonator and the carrier density dependence of all the parameters; in
addition, valence band mixing is included in the computation of the b
and structure. Both the total recombination rate due to spontaneous em
ission and the beta factor are computed and discussed. Numerical examp
les are reported for lambda/2 and lambda cavities since both of them p
resent interesting aspects. In particular for the second case the prob
lem of lateral radiation is investigated.