Subnanometer Control of the Heteroepitaxial Growth of Multimicrometer-Thick Ge / Si - Ge Quantum Cascade Structures

Abstract

Thick Ge/(Si,Ge) multiple-quantum-well heterostructures are interesting for silicon-integrated optoelectronic devices operating in the midinfrared and terahertz spectral regions. The epitaxy of such structures becomes increasingly challenging as their thickness increases, due to the accumulation of strain and defects. This study proves that ultrahigh-vacuum chemical vapor deposition allows for subnanometer control of the compositional profile throughout micrometer-thick strain-compensated multilayered structures with very low defect density. Here terahertz spectroscopy plus numerical simulation allows characterization at higher sensitivity and resolution than standard techniques.