Absorption coefficient for multiple-quasi fermi level system in quantum well

The absorption coefficients are necessary to determine the rate of radiative transition. In this work, absorption coefficient of one of the transition (transition from valence band to confined state in the quantum well) for a Multiple Quasi-Fermi level system (MQFL system) is derived from Fermi's golden rule while the other two absorption coefficients are calculated based on previously published work. The results are discussed with respect to AlInAs (barrier)/InAsP (well) quantum well system that is previously identified as one of the material combinations for a MQFL system. The results show the non-linear variation of absorption coefficients governing the transitions in the well (both from the confined states in the well to the continuum states and also from the valence band to the confined states) with the change in the quasi-Fermi level of the confined state. The results also show that the two absorption coefficients balance each other. As the carrier concentration in the confined states increase, the absorption coefficient for transition from the well to the continuum states increase while the absorption coefficient for transition from valence band to the confined states decrease and vice-versa. The results hence signify that provided the continuum states are coupled to the confined states only by radiative transition, it is possible to maintain a third quasi-Fermi level corresponding to the confined carriers and hence a MQFL system can be realized.