Pulsed-laser irradiation quantum well intermixing process in GaInAs/GaInAsP laser structures

We report the development and characterization of a postgrowth bandgap modification technique of GaInAs/GaInAsP laser structures utilizing a Q-switched Nd:YAG laser with a pulse length of approx. 8 ns and repetition rate of 10 Hz. Quantum well intermixing effect of the samples irradiated under pulsed energy densities of 2.8, 3.5 and 3.9 mJ mm^-2 at different exposure times was studied. A maximum bandgap shift of up to 112 meV has been observed from sample exposed to 3.9 mJ mm^-2 for 5 min after subsequent annealing in a rapid thermal processor at 625°C for 120 s. A spectrum broadening of 3 meV, relative to the as-grown sample, was obtained from intermixed sample exposed to 2.8 mJ mm^-2 for 1 min indicating that the quality of the material remains high. A differential bandgap shift of 60 meV has been obtained between a gold-masked region and laser-irradiated region. Lasers with bandgap tuned to 82 nm relative to the as-grown lasers have been fabricated using this technique.