Simple quasi-equilibrium model for quantum dash
(QDash) active material is derived for closely spaced energy states.
The model is used to study the differential gain of Qdash for
different key parameters. Expressions for the electron and the
hole occupation probabilities as a function of electron concentration
are derived. The derived analytical model shows excellent
agreement with numerical simulation. The differential gain of
Qdash active layer is calculated for different doping concentration
and different electron energy separation between adjacent states.
We find that when the electron energy states are widely separated,
the differential gain can be slightly enhanced at low-energy detuning
by doping the dashes by p-type doing. On the other hand,
our calculations reveal that when the electron energy states are
close to each other, doping the dashes by either n-type or p-type
concentration will not enhance the differential gain.