Suppression of thermal atomic interdiffusion in C-doped InGaAs/AlGaAs quantum well laser structures using TiO₂ dielectric layers

The effects of thermal annealing on C-doped InGaAs/AlGaAs quantum well laser structures capped with titanium dioxide (TiO₂) layers were investigated. The atomic interdiffusion was greatly suppressed by the presence of a TiO₂ capping layer during annealing, inhibiting even the thermal intermixing observed in the uncapped sample. An increase in the amount of lattice contraction associated with the presence of substitutional carbon C_As after annealing without a capping layer was observed, but not after annealing with a TiO₂ capping layer. Capacitance-voltage measurements confirmed the electrical activation of carbon after annealing without a dielectric layer and show a negligible change after annealing using a TiO₂ capping layer. The possible mechanisms involving both the atomic intermixing on the group III sublattice and carbon activation on the group V sublattice and the implications for optoelectronic device integration using impurity-free intermixing are discussed.