INFLUENCE OF BROADENING AND HIGH-INJECTION EFFECTS ON GAAS-ALGAAS QUANTUM WELL LASERS

Gain spectra and gain-current relations are calculated for GaAs-AlGaAs quantum-well lasers using a model which incorporates a phenomenological description of bandgap narrowing due to many-body effects at high injection, transition broadening by a carrier-density-dependent intraband scattering process, and broadening of the density of states function by fluctuations in the well width. The justification for including all these phenomena is made by examining spontaneous emission spectra observed through contact windows on quantum-well lasers. Using reasonable values of the parameters describing these effects, the model correctly predicts the observed lengthening of the laser emission wavelength with respect to the absorption edge, and correctly describes the variation of this wavelength, which has been observed for a set of devices with different numbers of quantum wells and the same well width. For a single GaAs quantum-well laser 25-angstrom wide, with the same parameters, the model predicts an increase in threshold current by a factor of 2.5 compared to an ideal quantum well without these effects.