Calibration Technique for MBE Growth of Long Wavelength InAlAs/InGaAs Quantum Cascade Lasers

Abstract

In this paper, we present the methodology for precise calibration of the Molecular Beam Epitaxy (MBE) growth process and achieving run-to-run stability of growth parameters. We present the analysis of the influence of fluxes stability during the growth of long wavelength quantum cascade laser structures designed for the range λ ~ 12–16 µm on wavelength accuracy with respect to desired emission wavelength. The active region of the lasers has a complex structure of nanometer thickness InxGa1−xAs/InyAl1−yAs superlattice. As a consequence, the compositional and thickness control of the structure via bulk growth parameters is rather difficult. To deal with this problem, we employ a methodology based on double-superlattice test structures that precede the growth of the actual structures. The test structures are analyzed by High Resolution X-ray Diffraction, which allows calibration of the growth of the complex active region of quantum cascade laser structures. We also theoretically studied the effect of individual flux changes on the emission wavelength and gain parameters of the laser. The results of simulations allow for the determination of flux stability tolerance, preserving acceptable parameters of the laser and providing means of emission wavelength control. The proposed methodology was verified by the growth of laser structures for emission at around 13.5 μm.