We report on stimulated emission at wavelengths up to 19.5 μm from HgTe/HgCdTe quantum well heterostructures with wide-gap HgCdTe dielectric waveguide, grown by molecular beam epitaxy on GaAs(013) substrates. The mitigation of Auger processes in structures under study is exemplified, and the promising routes towards the 20–50 μm wavelength range, where HgCdTe lasers may be competitive to the prominent emitters, are discussed.

The energy spectra of the mercury vacancy, the most common acceptor in HgCdTe material, is studied via numerical calculations and low temperature photoconductivity (PC) measurements of 'vacancy-doped' HgCdTe films with low cadmium content. Since the Hg vacancy is known to be a double acceptor, the model for the helium atom was adopted for degerate valence band of zinc blende semiconductors to classify the observed PC bands. This approach provides a fairly good description of the photoionization of both neutral and singly-ionized vacancy when the central cell potential is taken into account.

Due to their specific physical properties, HgCdTe-based heterostructures are expected to play an important role in terahertz photonic systems. Here, focusing on gated devices presenting inverted band ordering, we evidence an enhancement of the terahertz photoconductive response close to the charge neutrality point and at the magnetic field driven topological phase transition. We also show the ability of these heterostructures to be used as terahertz imagers. Regarding terahertz emitters, we present results on stimulated emission of HgCdTe heterostructures in their conventional semiconductor state above 30 THz, discussing the physical mechanisms involved and promising routes towards the 5–15 THz frequency domain.

We report on the stimulated emission (SE) from HgTe/CdHgTe quantum well (QW) heterostructures up to 240 K at 3.7 μm wavelength. Based on the temperature dependence of the SE threshold, a total Auger recombination (AR) coefficient of 10−27 cm6/s has been deduced for HgTe/CdHgTe QWs, which is much lower than that for bulk HgCdTe with the same bandgap and indicates suppression of (threshold) AR processes due to the symmetry of carrier dispersion curves. We demonstrate that QW-specific, non-threshold AR contributes strongly to the temperature quenching of laser action from HgTe/CdHgTe QWs. We expect, however, that the above processes may be partially suppressed via introduction of wide-gap CdHgTe barrier layers with a [Cd] fraction of 80% or higher. In this case, lasing up to at least 270 K at 3.7 μm wavelength seems feasible.

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We report stimulated emission in the 2.8-3.5 μm wavelength range from HgTe/CdHgTe quantum well (QW) heterostructures at temperatures available with thermoelectric cooling. The structures were designed to suppress the Auger recombination by implementing narrow (1.5 - 2 nm wide) QWs. We conclude that Peltier cooled operation is feasible in lasers based on such structures, making them of interest for spectroscopy applications in the atmospheric transparency window from 3 to 5 μm.

Interband photoluminescence (PL) and stimulation emission (SE) from HgTe/ HgCdTe quantum well (QW) heterostructures are studied in 5-20 mm wavelength range in regard to long-wavelength lasing applications. The authors obtain carrier lifetimes using time-resolved photoconductivity measurements and show that the dominating mechanism of carrier recombination changes from the radiative process to the non-radiative one as the bandgap is decreased, limiting the "operating" temperature for SE. The authors suggest that decreasing the QW width should reverse the balance in carrier recombination in favor of radiative processes and demonstrate 75 K improvement in the "operating" temperature in structure with narrower QW.of the band structure of narrow-gap HgTe/ HgCdTe heterostructures on carrier recombination mechanisms. [4] Recently, it was shown that HgCdTe-based QW can provide stimulated emission in the very longwavelength IR, [5] suggesting that such structures can be interesting for longwavelength emitters.At present moment, the best-performing semiconductor sources for far IR range are quantum cascade lasers (QCLs). They demonstrate ultimate figures of merit almost in the entire IR range. [6] The only "blind spot" of QCLs caused by the strong lattice absorption in traditional production materials (GaAs and InP) lies at wavelengths between 20 and 60 μm. InAs-based and Al-free QCLs are tackling this wavelength range from the mid-IR side, [7] while GaN QCLs have been proposed for frequencies above 5 THz. [8] However, interband lasers are also of interest since they are less demanding from the technological viewpoint and allow wavelength tuning with temperature. The cornerstone of effective light emitter, especially in far infrared range (FIR) range, is to suppress the non-radiative recombination, in

Recent progress in the molecular beam epitaxy (MBE) of CdHgTe/HgTe quantum well (QW) heterostructures paves the way to a new generation of photodetectors, light-emitting diodes and lasers [1,2]. A remarkable feature of such structures is the ability to suppress the Auger recombination in narrow (<10 nm) QWs in contrast to bulk-like wells [3]. In conjunction with a variable bandgap (from 0 to 1.5 eV), this feature allows developing long-wavelength lasers on interband transitions. Such lasers could be of use in 3.5-4.5 µm and 8-13.5 µm wavelength bands, corresponding to the atmospheric transparency windows, as well as in 25-50 µm range, where no quantum cascade lasers (QCLs) are available as yet. Coherent radiation from a HgCdTe (MCT) bulk alloy was first obtained in 1966 [4], 4 years after the very first semiconductor laser had appeared [5]. Interest in stimulated emission (SE) from MCT was revived in the 1990s [6,7], when the MCT growth technology was developing rapidly for the mid-infrared (IR) detectors [8]. However, this interest faded quickly, most likely due to the fast progress of mid-IR QCLs, happening about the same time. By 2015, the longest wavelength of coherent radiation obtained from MCT was 5.3 µm [6]. In recent years, some progress has been made as far as coherent radiation from MCT material is concerned [9][10][11]: in particular, SE up to ~20 µm has been demonstrated in [9]. The possibility of optical gain in HgCdTe QWs in 20-60 µm range has been already theoretically predicted [12]. However, for the development of lasers and photodetectors, scrutiny of carrier recombination is of paramount importance. CdHgTe/HgTe QW structures were poorly studied in this respect, especially as far as narrow-gap QWs are