Strain-balanced Si1-xGex/Si type II quantum wells for 1.55 μm detection and emission

This work deals with the optoelectronic properties of heterostructures built on type II Si1-xGex/Si strained quantum wells grown on relaxed Si1-yGey/Si (001) pseudo-substrates. To limit the intrinsic problem due to the real-space indirect nature of the interface, we propose and model three heterostructures having three different potential profiles of the valence and conduction bands which consist in various arrangements of Si and Si1-xGex barriers of different Ge contents. The proposed stacks are designed in a pragmatic way for a pseudomorphic growth on relaxed Si1-yGey assuming individual layer thickness being smaller than the known critical thickness and an overall compensation of the strain. Variation of thickness and compositions (x > y) permits to optimize i) the quantum confinement of electrons and heavy-hole levels and ii) the wave function's overlap and the out-of-plane oscillator strength. The optimum parameters satisfy a fundamental emission at a key 1.55 mu m wavelength below the absorption edge of each layer constitutive of the stacks. A comparison between the characteristics of the three heterostructures brings out the superior advantages of the W architecture.