Structural, optical, and electrical characterizations of a quantum cascade laser structure

Abstract

A quantum,cascade laser (QCL) is a new light source based on resonant tunneling and optical transitions between quantum mini-band states. QCLs are not only renewing the field of mid-infrared lasers but also represent a source of novel unconventional ideas for semiconductor lasers, in general. The structural, electrical, and optical characteristics of QCL samples with 30 periods of AlGaAs/GaAs grown by molecular beam epitaxy have been studied. By using transmission electron microscopy and double-crystal X-ray diffraction, we confirm that a superlattice structure can be intentionally grown in QCL samples. The full width at the half maximum of the 8-mum peak, which was observed by using Fourier transformed infrared absorption spectroscopy, was about 2-mum. By using deep-level transient. spectroscopy, a signal presenting about 100 meV activation energy was taken and this means that electrons in the ground state might jump to the next injector level which is between ground and excited level.