Qualitative estimation of optical gain in wide-band-gap semiconductor quantum wells

Room-temperature linear optical gain of a GaN quantum well is estimated qualitatively and is compared with optical gains of the ZnSe and GaAs quantum wells in order to examine the feasibility of GaN quantum-well lasers. Our analysis is based on the simple model using the density matrix method with parabolic band approximation. For 100 Å quantum wells, the calculated transparency level of a GaN quantum well (8.3×10¹⁸ cm ^-3) is slightly higher than that of a ZnSe structure (7.4×10¹⁸ cm^-3). But the transparency levels of GaN and ZnSe quantum wells are much higher than the transparency level of a GaAs quantum well (2.3×10¹⁸ cm^-3). It is expected that gain spectra of a GaN quantum well be narrower than those of a ZnSe quantum well.