Study of valence intersubband absorption in tensile strained Si/SiGe quantum wells

The hole subband structures and effective masses of tensile strained Si/Si_1 - y Ge_y quantum wells are calculated by using the 6\times 6 k \cdot p method. The results show that when the tensile strain is induced in the quantum well, the light-hole state becomes the ground state, and the light hole effective masses in the growth direction are strongly reduced while the in-plane effective masses are considerable. Quantitative calculation of the valence intersubband transition between two light hole states in a 7nm tensile strained Si/Si_0.55Ge_0.45 quantum well grown on a relaxed Si_0.5Ge_0.5 (100) substrates shows a large absorption coefficient of 8400 cm^ - 1.