Parasitic Recombination in a Laser with Asymmetric Barrier Layers

In a laser with asymmetric barrier layers (ABLs) two thin barrier layers adjacent to the active region on both sides are intended to prevent bipolar population of the waveguide layers, hence, to suppress parasitic recombination in them. A theoretical model of a laser with ABLs, based on rate equations which acknowledge undesirable carrier leakage inevitable in lasers of this type implemented in practice, is proposed. Solutions to equations are obtained for the steady-state case. By the example of an InGaAs/GaAs quantum-well laser (lasing wavelength λ = 980 nm), the effect of leakages through ABLs on the device characteristics is studied. The parasitic-flux suppression ratios C of ABLs which are required to prevent the adverse effect of waveguide recombination are estimated. In the case at hand, the effect of ABLs becomes appreciable at suppression ratios of C ≥ 102. To suppress 90% of the parasitic current, C should be 2.3 × 104. The effect of ABLs on useful carrier fluxes arriving at the active region is also studied.