Midinfrared electroluminescence of epitaxial PbTe quantum dots in CdTe with emission in the 2–3 μm wavelength range is demonstrated up to room temperature. The light-emitting diode structures were grown by molecular beam epitaxy with the active PbTe quantum dots embedded in the intrinsic zone of a CdTe/CdZnTe p-i-n junction on GaAs (100) substrates. The current and temperature dependences of the electroluminescence emission are presented. The comparison with photoluminescence measurements shows that midinfrared light-emission from the diodes originates from the quantum dots.

Optically pumped vertical external cavity surface emitting lasers (VECSELS) emitting in the mid-infrared range are demonstrated with an active structure based on PbTe quantum dots (QDs) embedded in CdTe. In contrast to Stranski-Krastanov QDs, the PbTe QDs are fabricated by a strain-free synthesis method consisting of a molecular beam epitaxy growth step followed by a post-growth-annealing step. The laser emission of the VECSELs covers a wavelength range between 3.5 and 4.3 μm by changing the temperature from 85 to 240 K. The threshold power is lower than 100  mW(P) and the output power is more than 50  mW(P) at low temperature.

Optical in-well pumped mid-infrared vertical external cavity surface emitting lasers based on PbTe quantum wells embedded in CdTe barriers are realized. In contrast to the usual ternary barrier materials of lead salt lasers such as PbEuTe of PbSrTe, the combination of narrow-gap PbTe with wide-gap CdTe offers an extremely large carrier confinement, preventing charge carrier leakage from the quantum wells. In addition, optical in-well pumping can be achieved with cost effective and readily available near infrared lasers. Free carrier absorption, which is a strong loss mechanism in the mid-infrared, is strongly reduced due to the insulating property of CdTe. Lasing is observed from 85 K to 300 K covering a wavelength range of 3.3–4.2 μm. The best laser performance is achieved for quantum well thicknesses of 20 nm. At low temperature, the threshold power is around 100 mWP and the output power more than 700 mWP. The significance of various charge carrier loss mechanisms are analyzed by modeling the device performance. Although Auger losses are quite low in IV–VI semiconductors, an Auger coefficient of CA = 3.5 × 10−27 cm6 s−1 was estimated for the laser structure, which is attributed to the large conduction band offset.

Tunable room-temperature mid-infrared photoluminescence emission from epitaxial PbSrTe quantum dots embedded in CdTe is demonstrated. By variation of the Sr content, the emission wavelength can be tuned over the whole 3 to 1.6 μm range. Comparing the emission of PbSrTe quantum dots, quantum wells and bulk material, a one order of magnitude increase in the emission efficiency is found for the quantum dots, contrary to the bulk behavior. Theoretical modelling of the transition energies shows that at higher Sr content, segregation of Sr into CdTe occurs. This conclusion is supported by annealing experiments.

Abstract. X-band microwave spectroscopy in a commercial EPR spectrometer at 1.5 K on modulation doped Si quantum well structures exhibits a relatively broad signal due to the coupled cyclotron-plasmon resonance, allowing to estimate both the carrier density and the electron mobility. After illumination above band gap, some of our heavily Sb-doped samples show a persistent splitting of this signal. Evaluation of the mobility yields a substantial increase of the mobility in the Si channel. Our results demonstrate that a major part of the scattering in the channel results from long range fluctuations of the Coulomb potential due to ionized donors in the doping channel. We attribute the substantial reduction in momentum scattering to screening of potential fluctuations within the doping layer by the additional carriers there.