[Paper Review] Feasibility of lasing in the GaAs Reststrahlen band with HgTe multiple quantum well laser diodes

А. А. Афоненко, Д. В. Ушаков+5 more|Digital Library of the Belarusian State University (Belarusian State University)|Oct 27, 2020

Spectroscopy and Laser Applications51 references9 citations

TL;DR

This paper proposes an electrically pumped laser diode based on multiple HgTe quantum wells in a Cd₀.₆Hg₀.₄Te barrier matrix, engineered to suppress Auger recombination for lasing at 26–30 μm. Using a comprehensive model including carrier transport, recombination, and thermal effects, the study demonstrates feasible lasing up to 90 K with pulsed output power reaching 8 mW.

ABSTRACT

Operation of semiconductor lasers in the 20--50 $μ$m wavelength range is hindered by strong non-radiative recombination in the interband laser diodes, and strong lattice absorption in GaAs-based quantum cascade structures. Here, we propose an electrically pumped laser diode based on multiple HgTe quantum wells with band structure engineered for Auger recombination suppression. Using a comprehensive model accounting for carrier drift and diffusion, electron and hole capture in quantum wells, Auger recombination, and heating effects, we show the feasibility of lasing at $λ= 26...30$ $μ$m at temperatures up to 90 K. The output power in the pulse can reach up to 8 mW for microsecond-duration pulses.

Motivation & Objective

• Address the lack of compact far-infrared sources in the 20–50 μm range, a gap caused by lattice absorption in GaAs-based QCLs and non-radiative recombination in interband lasers.
• Overcome the dominant limitation of Auger recombination in narrow-gap semiconductors by leveraging the unique band structure of HgTe quantum wells.
• Demonstrate the feasibility of electrically pumped lasing in the GaAs Reststrahlen band using HgTe multiple quantum wells with suppressed Auger recombination.
• Identify and analyze the key limiting factors—residual Auger recombination and Drude absorption—for temperature performance and output power.

Proposed method

• Design a heterostructure with 5.2 nm thick HgTe quantum wells embedded in Cd₀.₆Hg₀.₄Te barriers to achieve a bandgap tuned for 26–30 μm emission.
• Implement a comprehensive numerical model incorporating carrier drift and diffusion in barrier layers, capture into quantum wells, and radiative/non-radiative recombination.
• Use a 2D rate equation model for photon and carrier dynamics, including time-dependent modal gain, internal loss, and heat generation via Joule heating.
• Model thermal effects using Green’s functions for heat diffusion along the growth direction (z-axis), accounting for substrate, cladding, and heat sink layers.
• Calculate the 2D Auger coefficient using a parabolic band approximation for nonparabolic bands, with corrections for finite quantum well width via the K₂D/₃D factor.
• Solve the heat equation numerically to determine temperature rise during microsecond current pulses, with thermal diffusion length ~13 μm over 1 μs.

Experimental results

Research questions

• RQ1 Can electrically pumped lasing be achieved in the GaAs Reststrahlen band (20–50 μm) using HgTe multiple quantum wells?
• RQ2 To what extent does the band structure of HgTe quantum wells suppress Auger recombination compared to conventional semiconductors?
• RQ3 What is the maximum operating temperature for lasing in this HgTe-based structure, and what limits it?
• RQ4 What output power levels can be achieved under pulsed operation, and how do thermal effects influence performance?
• RQ5 How do residual Auger recombination and Drude absorption in doped regions affect the feasibility of lasing at elevated temperatures?

Key findings

• Lasing is feasible at 26–30 μm with an operating temperature up to 90 K, demonstrating the potential for electrically pumped FIR emission in the Reststrahlen band.
• The pulsed output power reaches up to 8 mW for microsecond-duration current pulses, indicating practical power levels for compact FIR sources.
• The 2D Auger coefficient is calculated as 8.3×10⁻¹² cm⁴/s at 70 K and 8.7×10⁻¹² cm⁴/s at 90 K, with the 3D equivalent at 9.0×10⁻²⁵ cm⁶/s and 9.4×10⁻²⁵ cm⁶/s, respectively.
• Residual Auger recombination in the quantum wells and Drude absorption in the highly doped injecting regions are identified as the primary limiting factors for temperature performance.
• The thermal diffusion length during a 1 μs pulse is ~13 μm, which is much larger than the active region thickness (~0.2 μm), justifying the 1D thermal model along the growth direction.
• The calculated overlap integral of Bloch wavefunctions is 0.3, and the K₂D/₃D factor is 0.4, indicating significant deviation from sinusoidal envelope approximations, which affects Auger coefficient accuracy.