Near-band-gap photoluminescence from pseudomorphic Si1−xGex single layers on silicon

Abstract

The systematic study of band-edge luminescence in pseudomorphic Si/Si1−xGex/Si double-heterostructure layers is reported for a wide composition range, 0.12<x<0.24, for the first time. An analytical expression for the exciton energy gap at 4.2 K valid for x<0.24 is derived from the no-phonon line energies: ESX(x) = 1.155−0.874x+0.376x2 eV. Addition of an expression for the exciton binding energy provides an approximation for the energy difference between the alloy valence band and the lowest conduction-band edge at low temperature. An exciton upshift of 16.9 meV due to quantum confinement is observed in a 6.3-nm Si0.83Ge0.17 alloy well. This is consistent with either type-I or type-II band alignment for which the conduction-band offset has a magnitude ‖ΔEc‖ ≤ 10 meV. The excitonic hole is closely confined in the alloy but the spectra suggest that the electron density in the silicon barriers is increased for the thin layer.

Optical properties of Si-Si1−xGex and Si-Ge nanostructures

“…The studies on the optical properties of quasi-2D Si-SiGe heterostructures have been focusing on material quality analysis [32][33][34][35][36][37] with a clear aim of searching for suitable artificial structures for fabricating cheap SiGe based optoelectronic devices and system. With such an aim in mind, much work has been done on the theory [6,8,9], growth [35,3839] and characterization [10][11][12][13][14] of ultrathin Sir,-G% (m + n = 10) superlattices and electroluminescence properties [40,41] of Si SiGe light emitting diodes.…”

Auger recombination in Si1‐xGex/Si quantum wells under high‐density photoexcitation

“…The samples were kept at 5 K during the measurements. Three prominent PL peaks appeared, which are assigned to the transverse optical (TO) and transverse acoustic (TA) phonon-assisted transitions, and the no-phonon-assisted (NP) transition [45], respectively.…”

Interwell coupling effect in Si/SiGe quantum wells grown by ultra high vacuum chemical vapor deposition

“…5. For a strained Si 1-x Ge x layer (x < 0.4) grown on Si substrate, the indirect bandgap E g at 4.2 K can be expressed as [14]:…”