Multi-step interrupted-growth MBE technology for GaAs/AlGaAs (∼9.4 μm) room temperature operating quantum-cascade lasers

Abstract

In order to adjust the highly controllable and optimum growth conditions, the multi-step interrupted-growth MBE processes were performed to deposit a series of GaAs/Al0.45Ga0.55As QCL structures. The additional calibrations of MBE system were carried out during the designed growth interruptions. This solution was combined with a relatively low growth rate of active region layers, in order to suppress the negative effects of elemental flux instabilities. As a result, the fabricated QCL structures have yielded devices operating with peak optical power of ∼12 mW at room temperature. That is a better result than was obtained for comparable structures deposited with a growth rate kept constant, and with the only initial calibrations performed just before the epitaxy of the overall structure.

Proton implantation for the isolation of AlGaAs/GaAs quantum cascade lasers

“…The structure used a double-plasmon Al-free waveguide for planar optical confinement. A detailed description of the relevant MBE-growth procedures can be found in [15][16][17]. The principle of the operation of the QCLs requires strictly determined thicknesses and compositions of individual layers as well as overall periodicity of the whole structure.…”

“…The laser operation is possible only when the designed structure is realized with the extreme technological precision of the geometrical and doping features. The presented laser structures were done with better than 1% thickness and at least 1% composition accuracy [15].…”

“…In this section, we describe the standard processing method by the deep etching process of the double-trench construction, in order to allow comparison with the novel method based exclusively on ion implantation. We also applied this standard method for the fabrication of a set of QCL devices [7,8,15] from the same epitaxial heterostructure that was used for testing the new solution. The standard processing technology comprised photolithography and a wet etching process (HCl:H 2 O 2 : H 2 O = 40:4:1) to the depth slightly beyond the active region.…”

“…The conductive edges of the laser can accelerate its damage by the possible appearance of short circuits. The main reason for this parasitic effect is that for high electrical power, The red arrow indicates the depth of electrical isolation, the performance of which is necessary in order to suppress the current spreading [15]. laser feeding the diffusion of the ohmic contact metal can proceed from the top of the device down along its edges.…”

Optical Properties of Active Regions in Terahertz Quantum Cascade Lasers

“…For more information about the reference sample (its structure and optical properties) the reader is referred to Refs. [13][14][15].…”