Room temperature photoluminescence of Ge-on-insulator structures formed by rapid melt growth

Abstract

Room temperature photoluminescence (PL) was observed along 50 μm long Ge strips on insulator on bulk Si substrates fabricated by rapid melt growth. The PL peaks evidently exhibited a redshift from the origin to the end of the Ge strip because of the shrinkage of the direct bandgap of Ge. Moreover, PL intensities increased along the direction of lateral epitaxial growth primarily because of the decrease in the energy difference between the direct and indirect gaps of Ge. The change in the Ge band structure, which facilitated changes in PL peaks and intensities, was found to have resulted from the variation of tensile strain ratios and Si fractions along Ge strips. Furthermore, the PL intensity at the end of the strip was one magnitude higher than that of bulk Ge, which indicates the high quality of Ge-on-insulator structures.