Electronic properties of Si/SiGe ultrathin quantum well superlattices

Abstract

PACS 73.21.Cd, 73.21.Fg Using the self-consistent and perturbative method of Jaros and the full potential linear muffin tin orbitals (FP-LMTO) method coupled to a plane wave (PLW) basis in the interstitial regions, we calculate the bandstructure of some ultrathin Si m /(SiGe) n quantum well superlattices, m and n being the numbers of atomic layers. The results show that in these systems the bandgap is indirect and that these superlattices have a type II potential configuration.

First principles calculation of the opto-electronic properties of (110) growth axis SiGe superlattices

“…We notice also significant changes in the CB behaviour near M, R and A: Energies become lower at R and higher at M and A for (110) compared with (001). We notice also that the present results for the (001) SL's differ significantly from those obtained previously with the same method [12]. These differences come from the CB's which are found to be very sensitive to the lattice parameter: In Ref.…”

“…These differences come from the CB's which are found to be very sensitive to the lattice parameter: In Ref. [12], the experimental lattice parameter was utilized directly in the bandstructure calculations while the one involved in the present calculations has been obtained by a minimization process. For the SL(3,3) systems, the (001) SL has its CB bottom at Z (an indirect bandgap of 0.490 eV) but occurs exactly at B in the (110) SL (an indirect bandgap of 0.379 eV).…”

“…In a recent work [12], Si/SiGe quantum well USL's were found to have a type II potential configuration (except for the unstrained USL, which is not realistic). The gap was always indirect in spite of a variation of the wavevector of the bottom of the CB, and utilizing a combination of the pseudopotential perturbative method of Jaros [13] and the first principles full potential linear muffin tin orbitals method (FPLMTO), the band line ups were calculated and found to be ∆E v = E VB (Ge) − E VB (Si) = 0.78 eV, which is in agreement with the value given in Ref.…”

“…The aim of the present work is to continue the above investigations on Si/SiGe USL systems [12,15], but considering now USL's having a (110) growth axis. The (001) growth axis Si/SiGe USL's have also been calculated for reasons of comparison.…”