MBE-grown InGaAs/GaAs quantum-dots on Ge substrate: An idea towards optoelectronic integration on silicon

We present a unique growth technique for molecular beam epitaxial growth of multi-layer InGaAs/GaAs quantum dots on Ge substrate. The optical and structural properties are compared with similar heterostructure grown on GaAs with the aim of achieving similar optical efficiency and structural homogeneity. An interesting phenomenon of increase in integrated photoluminescence (PL) intensity at high temperatures due to thermally assisted inter-dot carrier transfer is investigated using a coupled model and activation energy and quantum efficiency of dots is calculated for grown samples. The optical properties measured using steady state photoluminescence (PL) is found to quite similar to reference sample on GaAs substrate. Structural comparison performed using TEM shows good agreement between samples on Ge and GaAs substrate. H- ion-implantation is done on as-grown samples which further enhances optical properties.