Low-temperature molecular beam epitaxy growth of Si/SiGe THz quantum cascade structures on virtual substrates

Si/SiGe quantum cascade structures containing superlattice up to 100 periods have been grown on SiGe virtual substrates by using solid-source molecular beam epitaxy at low temperature. The surface morphology and structural properties of the grown samples were characterized using various experimental techniques. It has been concluded that the structures were completely symmetrically strained with high crystalline quality, precise layer parameters, and excellent reproducibility. Electroluminescence was observed with peaked intensity at ∼3 THz at both 4 and 40 K, which agrees very well with expected interwell intersubband transition according to the design.