Design and Preparation of AlN/GaN Quantum Wells for Quantum Cascade Laser Applications

An envelope function framework was used to calculate the conduction band structure of AlN/GaN quantum wells for application to quantum cascade lasers. We took into account the piezo- and spontaneous polarization fields in the nitride quantum wells. The design of the quantum cascade structures in the AlN/GaN system becomes much simpler if we utilize the effect of polarization fields. [(AlN)1/(GaN) n1] m /(AlN) n2 quantum wells were prepared using hot-wall epitaxy for mid-infrared quantum cascade laser applications, and X-ray diffraction and transmission electron microscopy (TEM) measurements were performed on them. The X-ray diffraction measurements of the quantum wells were in good agreement with the theoretical pattern, and the coherent growth of quantum wells on the GaN buffer layers was ascertained by X-ray reciprocal mapping. The existence of a single atomic layer of AlN was observed by TEM measurements.