Optical Gain Characteristics in GaAsPN/GaPN Quantum Well Lasers for Silicon Integration

Optical gain characteristics of strain-compensated GaAsPN/GaPN quantum wells (QWs) with the GaPN barrier under 1.0 % tensile strain were investigated using the multiband effective-mass theory and the non-Markovian gain model. The transition energy linearly increases from 1.12 to 1.22 eV when P content ratio changes from 0.1 to 0.4. The theoretical transition energy reasonably agrees with the experiment. The Coulomb enhancement ratio, g_many/g_free, decreases with increasing compressive strain because the average hole effective mass decreases with increasing strain. As a result, the QW structure with a smaller compressive strain has larger optical gain than that with a larger compressive strain for higher carrier densities. On the other hand, in the case of smaller carrier densities, the QW structure with a larger compressive strain shows larger optical gain than that with a smaller compressive strain because the former has larger optical matrix element producted by Kane's parameter and quasi-Fermi level separation than the latter. The absolute value of the bandgap renormalization increases with increasing carrier density and is about 99 meV at 5 × 10¹² cm^-2, which is slightly larger than that of GaAs-based or InP-based QW structures.