OPTICAL-DETECTION OF INTERDIFFUSION IN STRAINED SI1-XGEX SI QUANTUM-WELL STRUCTURES/

An extended optical study on interdiffusion in strained Si1-xGex/Si qu antum well structures grown by gas-source molecular beam epitaxy is pr esented. Using photoluminescence (PL) spectroscopy, diffusion coeffici ents are derived from the luminescence peak energy blue shifts observe d in vacuum-annealed samples. Here, growth temperature dependence of t he diffusion coefficients is systematically investigated and it is fou nd that the activation energy associated with interdiffusion is rather constant at approximately 3 eV. In addition, extended results are pre sented to support the oxidation-induced band gap shrinkage observed as the anomalous red shift in samples annealed in N2 or O2 ambient. The strain originating from the oxidation of the capping layer is estimate d from the energy shifts. Excitation power dependence of PL intensity is investigated to study the eff ect of thermal treatment on the cryst al quality. It is found here that surface oxidation in QWs with thin c apping layer degrade their optical quality.