SELECTIVE INTERDIFFUSION OF GAINAS/ALLNAS QUANTUM-WELLS BY SIO2 ENCAPSULATION AND RAPID THERMAL ANNEALING

Substantial blue shifts in the photoluminescence (PL) transition energies of GaInAs/AlInAs single quantum wells were observed due to localized SiO 2 capping and rapid thermal annealing at temperatures between 750 and 900 °C. Secondary-ion mass spectroscopy analyses show that the blue shifts are caused by the impurity-induced interdiffusion of the quantum well interfaces due to the simultaneous diffusion of silicon and oxygen into the crystal. The selective intermixing occurred in regions capped with SiO2 and exhibited blue shifts up to 74 meV while regions with no SiO2 showed only minimal shifting. With this band gap change, a lateral index change of approximately 0.6% is anticipated, making this process suitable for index-guided structures. Samples also exhibited up to 26-fold increases in PL efficiencies due to the annealing process. The dependence of energy shifts and PL efficiencies are studied by measuring room-temperature and low-temperature (≊80 K) photoluminescence. Interdiffusion coefficients have also been calculated as a function of temperature.