GaInAs/ AlAsSb quantum cascade lasers: A new approach towards 3-to-5 µm semiconductor lasers

At present GaInAs/AlInAs based quantum cascade (QC) lasers represent the state-of-the-art with respect to the short-wavelength (< 5 µm) performance of the QC laser concept. This performance, however, is intrinsically limited by the available conduction band offset of 0.5-0.7 eV, thus motivating research on materials combinations with larger band offsets, such as GaN/AlN and InAs/AlSb. A particularly attractive materials combination is GaInAs/AlAsSb grown lattice-matched on InP. It offers a gamma-point conduction band offset of about 1.6 eV, while the mature growth and processing technologies available for InP-based lasers can be used and the favorable properties of InP as a waveguide cladding material can be exploited. In this paper recent advances in GaInAs/AlAsSb QC laser research will be reviewed, leading to a maximum pulsed operating temperature of > 400 K for devices emitting at 4.6 µm and an impressive maximum peak output power of 8 W at 77 K (corresponding to a total power efficiency of 23 %) for a QC laser emtitting at 3.7 µm. Furthermore, current limitations of the GaInAs/AlAsSb QC laser concept and challenges for future research are discussed.