Quantum-confined direct band transitions in tensile strained Ge/SiGe quantum wells on silicon substrates

Abstract

We directly demonstrate quantum-confined direct band transitions in the tensile strained Ge/SiGe multiple quantum wells grown on silicon substrates by room temperature photoluminescence. The tensile strained Ge/SiGe multiple quantum wells with various thicknesses of Ge well layers are grown on silicon substrates with a low temperature Ge buffer layer by ultrahigh vacuum chemical vapor deposition. The strain status, crystallographic, and surface morphology are systematically characterized by high-resolution transmission electron microscopy, atomic force microscopy, x-ray diffraction, and Raman spectroscopy. It is indicated that the photoluminescence peak energy of the tensile strained Ge/SiGe quantum wells shifts to higher energy with the reduction in thickness of Ge well layers. This blue shift of the luminescence peak energy can be quantitatively explained by the direct band transitions due to the quantum confinement effect at the Gamma point of the conduction band.

Observation of improved minority carrier lifetimes in high-quality Ge-on-insulator using time-resolved photoluminescence

“…Using B 1.0 for high Ge mole fractions as in Ref. [19], the Ge mole fraction of the top interface of GOI2 is 0.86. Note that this intensity ratio method only gives information on an averaged composition over the penetration depth of the 514-nm excitation source.…”

1.55 μm direct bandgap electroluminescence from strained n-Ge quantum wells grown on Si substrates

“…Tensile-strained Ge QWs have demonstrated direct-gap transitions. 8,9 In this work, electroluminescence from strained 10 period n-Ge multiple quantum well (MQW) LEDs grown directly on a silicon wafer is presented which produces electroluminescence at the important 1.55 lm wavelength at room temperature (298 K).…”

Recent progress in GeSi electro-absorption modulators

“…In 2011, Ren et al [44] experimentally demonstrated that Ge/Si 0.15 Ge 0.85 MQWs on a Si 0.1 Ge 0.9 relaxed buffer can provide optical modulation from light wavelengths of 1450–1550 nm with an applied electric field of as high as 20 V μ m −1 . Additionally, application of tensile strain can be used to obtain Ge QWs with direct gap transition around 1.55 μ m. Chen et al [45] and Carroll et al [46] prepared tensile-strained Ge/SiGe MQWs through tensile-strained Ge virtual substrate, and showed direct-gap excitonic transition around 1.55 μ m from the photoluminescence and transmission spectra at room temperature. To our knowledge, no QCSE has yet been demonstrated from such an approach.…”