Photoluminescence of Si_1-xGe_x/Si Quantum Well Structures

Abstract

Photoluminescence (PL) spectra of Si 1- x Ge x /Si multiple quantum wells (MQW) grown by molecular beam epitaxy (MBE) have been investigated. Strong emission bands appear for all the as-grown samples. The PL intensity is increased by a factor of 5-10 after the annealing at 600-700°C. The annealing at 800°C results in the disappearance of the strong emission bands. The dependence of the PL intensity on the excitation power density indicates that some recombination center is involved in the strong emission. Annealing effects of the PL spectra can be explained as the behavior of this recombination center under the heat treatments. Transmission electron microscopy (TEM) observations show that the quality of the quantum well structures is related to the observed PL characteristics. The intense PL may be due to the two-dimensional carrier confinement.