Direct Band Gap Of Ge Research Articles

Temperature and Isotopic Mass Dependence of the Direct Band Gap in Semiconductors: LCAO Calculations

Using perturbation theory, within a tight-binding (LCAO) approach, we have calculated the effects of electron–phonon interaction on the lowest direct band gap of Ge, GaAs and ZnSe. The agreement of the calculated temperature coefficient with experimental data is satisfactory. Following our approach, we have also calculated the dependence of the direct band gap on isotopic mass. The results are in close agreement with the experimental data.

Piezoreflectance of strained Si/Ge superlattices grown on Ge(001)

We have studied the piezoreflectance (PzR) and photoreflectance (PR) spectra at 77 K of a series of short-period Si/Ge superlattices grown on Ge(001) substrates. These samples are similar to those measured using electroreflectance (40 K) by Pearsall et al. [Phys. Rev. Lett. 63 (1989) 2104]. We have observed several low-energy features in the PzR data just above the direct band gap of Ge. They are clearly due to quantum-confined direct transitions in the Ge spacer region, not pseudodirect transitions in the short-period Si/Ge portion of the samples as reported by Pearsall et al.

Piezoreflectance study of short-period strained Si-Ge superlattices grown on (001) Ge.

We have studied the stress-modulated reflectivity at 77 K of a series of short-period strained Si-Ge superlattices grown on (001) Ge substrates. These samples are similar (or identical) to those measured using electroreflectance (40 K) by Pearsall et al. [Phys. Rev. Lett. 63, 2104 (1989)]. We have detected several low-energy features just above the direct band gap of Ge. The observed spacer-layer-thickness dependence of the transition energies and comparison to a calculation clearly show that they are due to quantum-confined direct transitions in the Ge spacer region, not pseudodirect transitions in the short-period Si-Ge portion of the samples.