Search

X-ray diffraction investigations of type II InAs/GaSb superlattice on a GaSb(001) substrate are presented. The wide range of diffraction angles (2θ/ω scans) covering 002 and 004 reflections was examined at Petra III synchrotron. The angular region between 002 and 004 reflections was the most interesting part of the measured diffraction profile. In this region, a non-coincidence of superlattice satellite peaks belonging to these two reflections is observed. The multiple-beam dynamical diffraction approach was used for correct simulation of the observed diffraction profile. [ABSTRACT FROM AUTHOR]

In this paper, the X-ray diffraction profiles of Quantum Cascade Laser (QCL) structures have been investigated. The examined structures were grown by molecular beam epitaxy. The crystallographic characterization was carried out using high resolution X-ray diffractometer. The information about thickness of individual layers and periodicity of the structures was derived from simulation of diffraction profiles calculated using dynamical diffraction theory. The influence of interface roughness on the shape of satellite peaks was studied. The particular attention has been paid to the analysis of the broadening of satellite peaks. The presented results show that broadening is due to the variation of thickness of individual layers. [ABSTRACT FROM AUTHOR]

In this paper, we report the results of investigation of 9.5 µm AlGaAs/GaAs and strain compensated 4.7 µm AlInAs/InGaAs/InP QCLs. We also show the results for 9.5 µm lasers based on lattice matched AlInAs/InGaAs/InP structures. The developed GaAs/AlGaAs lasers show the record pulse powers of 6 W at 77 K and up to 50 mW at 300 K. This has been achieved by careful optimization of the MBE growth process and by applying a high reflectivity metallic coating to the back facet of the laser. The 9.5 µm AlInAs/InGaAs/InP lasers utilize AlInAs waveguide and were grown exclusively by MBE without MOCVD regrowth. The short wavelength, strain compensated QCLs were grown by MOCVD. They represent state-of-the-art parameters for the devices of their design. For epitaxial process control, the atomic-force microscopy (AFM), high resolution X-ray diffraction (HR-XRD) and transmission electron microscopy (TEM) were used to characterize the morphological and structural properties of the layers. The basic electro-optical characterization of the lasers is provided. We also present results of Green's function modeling of mid-IR QCLs and demonstrate the capability of non-equilibrium Green's function (NEGF) approach for sophisticated but still computationally effective simulation of laser's characteristics. [ABSTRACT FROM AUTHOR]

We have studied the influence of the beryllium doping on strain in the II-type InAs/GaSb superlattices (SLs) by means of high-resolution X-ray diffraction (HRXRD). Three analyzed superlattices were grown by molecular beam epitaxy. One of the examined superlattices was undoped. Two others structures, called doped SLs, composed of two superlattices: Be-doped and undoped which were grown one on the top of each other. The doping concentration was determined by secondary ion mass spectroscopy. The doping level was 1×10 cm and 2×10 cm. For doped superlattices, the HRXRD measurements showed splitting of satellite (ST) peaks. Furthermore, the separation of ST peaks increase with doping level. In contrast, for undoped superlattice, the splitting of the ST peaks was not observed. Sometimes the separation of ST peaks can be caused by change of thickness period of superlattice or partial relaxation of the structure. However, we claim that in our experiment the splitting is caused by another mechanism: The presence of Be atoms in SL causes the change of average lattice constant of the superlattice. The influence of Be dopant on lattice parameter of superlattice was confirmed by theoretical simulations. Furthermore, the change of the lattice constant (Δ a/ a) of the GaSb:Be buffer was examined. The reduction of lattice parameter of GaSb was noticed. It was caused by the presence of Be doping and unintentionally incorporated As-atoms in the GaSb layer. It is very important to know that even very small Be concentration (1×10 cm) causes the change of average lattice parameter of SL. [ABSTRACT FROM AUTHOR]