Abstract
This paper presents the results of conduction band discontinuities calculation for strained/relaxed Si1-xGex/Si1-yGey heterointerfaces in Gamma(15C), Gamma(2'C) and L upper bands minima, as well as the room-temperature strained (vs. relaxed) band gaps deduced from the classical model-solid theory. Based upon the obtained data, we propose a type-I W-like Si1-yGey/Si1-xGex/Ge/Si1-xGex/Si1-yGey quantum wells heterostructure optimized in terms of compositions and thicknesses. Electronic states and wave functions are found by solving Schr " odinger equation without and under applied bias voltage. An accurate investigation of the optical properties of this heterostructure is done by calculating the energies of the interband transitions and their oscillator strengths. Moreover, a detailed computation of the bias-voltage evolution of the absorption spectra is presented. These calculations prove the existence of type-I band alignment at Gamma(2'C) point in compressively strained Ge quantum wells grown on relaxed Ge-rich Si1-yGey buffers. The strong absorption coefficient (> 8x10(3) cm(-1)) and the large Stark effect (0.1 eV @ 2 V) of the Gamma(2'C) transitions thresholds open up perspectives for application of these heterostructures for near-infrared optical modulators.