Characterization of AlN/GaN Quantum‐Cascade Structures Prepared by Hot‐Wall Epitaxy

Abstract

[(AlN)1/(GaN)n1]m/(AlN)n2 quantum-cascade (QC) structures were prepared by hot wall epitaxy for midinfrared laser application, periodically inserting several atomiclayers of AlN into (AlN)1/(GaN)n1 short period superlattices. The (AlN)1/(GaN)n1 short-period superlattice has a large first-subband broadening, and effective population inversion between first and second subbands is expected through the electron injection into the second subband. The AlN/GaN quantum-well system grown to [0001] direction shows a large piezo-electric effect, and the effective electron injection into the second subband is expected by the periodically inserted AlN layers. The QC structure was characterized by X-ray diffraction, transmission electron microscopy (TEM). The (0002) X-ray diffraction pattern showed good agreement with the theoretical one, and (10—14) reciprocal mapping of the cascade structure showed the QC structure was grown coherently on the GaN buffer layer.