Mid-IR quantum cascade lasers: Device technology and non-equilibrium Green's function modeling of electro-optical characteristics

TLDR

The study presents NEGF modeling of mid‑IR QCLs, demonstrating its capability for sophisticated yet computationally efficient simulation of laser characteristics. The devices were fabricated by MBE and MOCVD, characterized with AFM, HR‑XRD, TEM, and electro‑optical measurements, and modeled using a non‑equilibrium Green’s function approach. The authors report record 6 W pulse power at 77 K and 50 mW at 300 K for GaAs/AlGaAs QCLs, along with state‑of‑the‑art performance for 4.7 µm and 9.5 µm AlInAs/InGaAs/InP structures.

Abstract

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.