Influence of broadening and barrier recombination on the operation of short-wavelength GaAs/AlGaAs quantum well lasers

Examination of the spontaneous emission spectra of GaAs/AlGaAs quantum well lasers with 25 Angstrom wide wells show that a realistic model of quantum well gain should include band gap renormalization and broadening due to intraband scattering and fluctuations in the well width of ± 1 monolayer. Such a model has been used to obtain a correct description of laser wavelength as a function of gain. For parameter values describing the authors' samples, the model predicts that the broadening due to monolayer fluctuations in the well width has a similar effect on the threshold current of a 2 x 25 Angstrom laser as the broadening due to intraband scattering, and that the threshold current is about 2.5 times greater than without broadening. The calculations also predict a linear temperature dependence of threshold current between 200K and 400K. Since the principal effect of the broadening is to increase the threshold current, the value of the parameter To is predicted to increase to about 400K compared with about 320K without broadening. Non-radiative recombination processes in the AlGaAs barriers are shown to have the dominant effect on the temperature sensitivity above 300K, lowering the To to about 138K using a non-radiative recombination time of 3ns