Wave function engineering in W designed strained-compensated Si/Si1−xGex/Si type II quantum wells for 1.55 μm optical properties

During the past decade, ultra-short period SinGem zone-folded superlattices and Ge/Si quantum dots have been investigated as building blocks for potential light emitting devices compatible with the on-chip CMOS technology. The aim of these nanostructures is to overcome the k-space indirect nature of the bandgap. Strangely, few attentions have been paid to the conventional and less sophisticated quantum well (QW) approach for emission. To limit at first the problems inherent to the real space indirect character of the type II interface in this system of material, we propose a Si/Si1−xGex/Si strained double QW embedded in relaxed Si1−yGey barriers. The conduction and the valence bands present a W-like potential profile, resulting in a quasi-type I heterostructure. The thickness and compositions (x > y) of this single W-QW are computed in order to get (i) the optimum quantum confinement of single electrons and heavy-holes levels, (ii) the optimum out of plane oscillator strength and wave functions overlap and (iii) the requested fundamental emission at a key 1.55 μm wavelength below the absorption edge of each constitutive materials. Furthermore, the structure is designed in a realistic way for epitaxial growth assuming strain compensation on relaxed Si1−yGey and thickness of each layer being smaller than the known critical thickness.