Photoluminescence in Si1−x−yGexCy alloys

Abstract

We report photoluminescence from Si1−x−yGexCy films grown epitaxially on Si (100) by chemical vapor deposition. We observe significant energy shifts but no dramatic changes in the photoluminescence line shape caused by the presence of carbon. Using standard deformation potential theory to correct the epitaxial strain shifts, we conclude that the band gap of relaxed Si1−x−yGexCy alloys has a lower energy than the band gap of relaxed Si1−xGex with the same Si/Ge ratio. We propose an explanation of these results based on the assumption that carbon forms a resonant level within the conduction band of Si1−xGex.

Synthesis and Atomic and Electronic Structure of New Si−Ge−C Alloys and Compounds

“…In fact, for C concentrations of ∼1 atom %, the band gap of Si 1-x-y Ge x C y alloys has been found by photoluminescence to have a lower energy than that of Si 1-x Ge x with the same Si:Ge ratio (see Figure 19). 60 Nevertheless, HBTs have been fabricated using Si 1-x-y Ge x C y and initial results indicate a slight increase in band gap (by 26 meV/% C). 61 Photoluminescence studies have shown 52 that band gaps in strained Si 1-x C x /Si quantum well structures decrease slightly with increasing C concentration up to ∼1.5 atom % C. The band gap reduction in this system is, however, attributed to the large tensile strain that must exist within the alloy layers, and this lowers the energy of the D-electron valleys oriented in the growth direction.…”

“…However, a corresponding increase in band gap, assuming the average band structure between Si−Ge and diamond as suggested by Soref, is not observed. In fact, for C concentrations of ∼1 atom %, the band gap of Si 1- x - y Ge x C y alloys has been found by photoluminescence to have a lower energy than that of Si 1 - x Ge x with the same Si:Ge ratio (see Figure ) . Nevertheless, HBTs have been fabricated using Si 1- x - y Ge x C y and initial results indicate a slight increase in band gap (by 26 meV/% C) …”

“…Figure19. Low-temperature photoluminescence spectra from Si0.79Ge0.20C0.01/Si (dotted line) and Si0.80Ge0.20/Si (solid line) grown by CVD 60. …”

Photoluminescence in SiCGe thin films grown on 6H-SiC

“…One of the most studied heterostructure consists of compressively strained Si 1 À x Ge x layers grown on silicon. Several groups also investigated the PL properties of the SiCGe layers [10][11][12], but such SiCGe layers are grown on Si substrate. To our knowledge, no PL properties of the SiCGe/SiC heterostructure have been presented in the literature.…”

Photoluminescence of Tensile Strained, Exactly Strain Compensated, and Compressively StrainedSi1−x−yGex

“…The Raman results indicate that the Si-Si bonds are not identical to those in unstrained bulk Si for strain compensated Si 12x2y Ge x C y alloys which have the same average lattice constant [11]. Lorentzen et al [12] discussed the possibility of band gap lowering in SiGeC due to Cinduced localized energy levels. Further experiments, especially for samples with higher C concentrations, will be required to determine the exact contributions in band gap shift due to band structure changes, on the one hand, and localized energy levels, on the other hand.…”