InAs or InGaAs quantum well laser structures have been grown on InP-based metamorphic In0.8Al0.2As buffers by gas source molecular beam epitaxy. The effects of barrier and waveguide layers on the material qualities and device performances were characterized. X-ray diffraction and photoluminescence measurements prove the benefits of the strain compensation in the active quantum well region on the material quality. The device characteristics of the lasers with different waveguide layers reveal that the separate confinement heterostructure plays a crucial role on the device performances of these metamorphic lasers. Type-I emissions in the 2–3 µm range have been achieved in these InP-based metamorphic antimony-free structures. By combining the strain-compensated quantum wells and separate confinement heterostructures, the laser performances have been improved and laser emission up to 2.7 µm has been achieved.
Impurities and their influence on the properties of InAs single crystals have been studied by combining the results of glow discharge mass spectrometry (GDMS), Hall measurements, Raman scattering and infrared absorption. The results indicate that carbon is a major impurity in LEC-InAs single crystals and exhibits a significant influence on the electrical and optical properties.
We report the first photoluminescence (PL) characterization of InAs nanowires (NWs). The InAs NWs were grown on GaAs B and Si substrates using the Au-assisted molecular beam epitaxy (MBE) growth technique or metal-organic chemical vapor deposition (MOCVD). We compared the PL response of four samples grown under different conditions using MBE or MOCVD. High-resolution transmission electron microscopy (HRTEM) and selected area electron diffraction (SAED) patterns were utilized to determine the crystal structure and growth directions of the NWs to relate PL features to NW structural parameters. We observed mainly three PL peaks which were below, near and above InAs bandgaps, respectively. Temperature and excitation intensity dependence PL measurements were also performed to help elucidate the origins of the PL peaks of NWs. Of particular interest was a band-edge emission peak that was blue-shifted due to quantization effects of the InAs NWs, as confirmed by our calculation.
Undoped InAs and InAs p-n junction epitaxial layers were grown on (100)-cut InP substrates with molecular beam epitaxy. The lattice difference between the substrate and the InAs layers was matched with a graded AlInAs buffer layer. The alloy composition, structural characteristics and carrier mobility of the structures were determined from the high-resolution x-ray diffraction, atomic force microscopy and Hall-effect measurements, respectively. The optical parameters of the layers were characterized by the emission of terahertz (THz) pulses when the samples were illuminated with femtosecond laser pulses. It has been found that the built-in electric field in the p-n junction enhances the THz emission. Registering THz signals in the quasi-reflection direction, the p-n junction emits more intense radiation in comparison to an undoped bulk InAs. At excitation wavelengths >1.8 μm the InAs p-n junction provides stronger THz pulses than those from (111)-cut p-InAs, the best surface THz emitter known to date. The epitaxial layers were also exposed to a constant magnetic field from neodymium permanent magnets, which further enhances THz emission and allows registering THz radiation in the line-of-sight terahertz time-domain-spectroscopy geometry.