Terahertz intersubband absorption and conduction band alignment inn-type Si/SiGe multiple quantum wells

Abstract

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