2.3 µm InGaAsSb/AlGaAsSb Quantum-Well Laser Diode via InAs/GaSb Superlattice Layer on GaAs Substrate

We present 2.3 μm InGaAsSb/AlGaAsSb type I laser diodes (LDs) on GaAs substrate; a superlattice (SL) layer was introduced as an interconnecting layer playing an important role in manipulating the optical field distribution and reducing free-carrier absorption in multiquantum wells (MQWs) for achieving balanced and optimal LDs performance. Accordingly, power of 8.6 mW was obtained with 2.3 μm wavelength. Our results demonstrate that superlattice layer may open a new avenue for high performance and improvement in mid-infrared laser diode.

Experimental Study of Phonon-Folding in Si/Ge and Si/Sige Structures Designed for Thermoelectric Applications

We report data of Raman study of Si/Ge and Si/SiGe superlattices designed for thermoelectric applications. The obtained Raman spectra clearly indicate the presence of folded doublets from longitudinal acoustic phonons. Due to the significant difference in the sound velocities for Si and Ge the position of the doublets strongly depends on the superlattice layer thickness and ordering. Comparison of the Raman data for different samples with measured thermal and thermoelectric properties allows us to determine a correlation between the strength of the phonon confinement in these structures and their thermoelectric properties. Our experimental results are consistent with recent theoretical prediction of increased thermoelectric figure of merit in semiconductor quantum wells.