InGaAs/InAlGaAs injection lasers grown on GaAs substrates

Epitaxy of lattice-mismatched systems is of current interest due to the importance of the device applications for such structures.1 In the laser area, GaAs injection lasers grown on Si substates have been demonstrated in both pulsed and cw modes,2,3 results that have important implications for wafer-level integration of optical and electronic devices. Lasers consisting of InGaAs layers grown on GaAs are of interest because of the flexibility they would afford in wavelength selection. One viable approach is the use of strained (pseudomorphic) InGaAs quantum wells in the laser active region with the rest of the structure consisting of GaAs and AIGaAs.4 We report the results of an alternative approach in which all the layers of the laser structure are lattice matched to each other but mismatched relative to the GaAs substrate. One major technical challenge in this approach is to limit the propagation of threading dislocations (resulting from the mismatch) into the laser active region, so that threshold currents are low.