Terahertz intersubband absorption and conduction band alignment in n-type Si/SiGe multiple quantum wells.

Absorption due to conduction intersubband transitions is studied in n-type s-Si/SiGe multiquantum wells (MQW) of different well widths and barrier composition grown by UHV-chemical vapor deposition (CVD). The measured intersubband transition energies are compared with the theoretical results of a tight-binding model which provides the electronic band structure of the complete MQW system throughout the whole Brillouin zone. Our findings demonstrate both the high quality of the CVD grown MQWs and the effectiveness of the adopted tight-binding model in describing band profiles and electronic structures of SiGe multilayer systems. In particular we have evaluated the conduction band offsets in the investigated structures.