We compare the heat extraction efficiency for a standard Vertical External Cavity Surface-Emitting Laser and the distributed Bragg reflector (DBR)-free structure employing a single and double diamond heat-spreaders, respectively. Both heterostructures grown by Molecular Beam Epitaxy employ two identical active regions designed for emission at 980 nm. We show that the thermal resistance has been decreased 15 times when there is no DBR and heat is extracted from both side of active region. For DBR-free laser no thermal rollover of power conversion characteristic was observed in the range of considered input powers.

Indium-based micro-bump arrays, among other things, are used for the bonding of infrared photodetectors and focal plane arrays. In this paper, several aspects of the fabrication technology of micrometer-sized indium bumps with a smooth surface morphology were investigated. The thermal evaporation of indium has been optimized to achieve ~8 μm-thick layers with a small surface roughness of R_a = 11 nm, indicating a high packing density of atoms. This ensures bump uniformity across the sample, as well as prevents oxidation inside the In columns prior to the reflow. A series of experiments to optimize indium bump fabrication technology, including a shear test of single columns, is described. A reliable, repeatable, simple, and quick approach was developed with the pre-etching of indium columns in a 10% HCl solution preceded by annealing at 120 °C in N₂.

In this paper, we have examined the influence of electroplated gold thickness on the thermal and electro-optical properties of mid-IR AlInAs/InGaAs, InP QCLs. The experimental results show a significant reduction of the temperature of QCL active region (AR) with increasing gold layer thickness. For QCLs with 5.0 μm gold thickness, we observed a 50% reduction of the active region temperature. An improvement of key electro-optical parameters, that is, threshold current density and maximum emitted power for structures with thick gold, was observed. The results of micro-Raman characterization show that the electroplated gold layer introduces only moderate compressive strain in top InP cladding, which is well below the critical value for the creation of misfit dislocations.

We report recent results of works on quantum cascade lasers at the Institute of Electron Technology. During that time we have developed technology of lasers emitting at wavelengths 9.0–9.5 μm and 4.7 μm, based on InGaAs/AlGaAs/GaAs and InAlAs/InGaAs/InP heterostructures; both lattice matched and strain compensated. The structures were grown by molecular beam epitaxy MBE and by metalorganic vapor phase epitaxy MOVPE. The InGaAs/AlGaAs/GaAs lasers were grown by MBE. For InP based lasers three types of structures were investigated; the one grown exclusively by MBE without MOVPE overgrowth, the second fabricated by hybrid approach combining MBE grown AlInAs/InGaAs active region with MOVPE grown InP top waveguide layer and the third one with both the top and the bottom InP waveguide grown by MOVPE. Regardless of the waveguide construction, the active region was grown by MBE in every case. The lasers were fabricated in double trench geometry using standard processing technology. The buried heterostructure lasers were also investigated.