In this work, we demonstrate the features of a two-stage epitaxial growth technique and show the results of power and efficiency measurements for three different designs of quantum cascade lasers with a record-high peak power in the 8 $\mathsf{\mu }$m spectral region. The time-resolved QCL spectral study proves that InP-based upper cladding paired with an InP contact layer provides better heat dissipation and allows one to reach better power characteristics in comparison with InGaAs-based contact, even with short pulse pumping.

We study recombination processes in nitride LEDs emitting from 270 to 540 nm with EQE ranging from 4% to 70%. We found a significant correlation between the LEDs’ electro-optical properties and the degree of nanomaterial disorder (DND) in quantum wells (QWs) and heterointerfaces. DND depends on the nanoarrangement of domain structure, random alloy fluctuations, and the presence of local regions with disrupted alloy stoichiometry. The decrease in EQE values is attributed to increased DND and excited defect (ED) concentrations, which can exceed those of Shockley–Read–Hall defects. We identify two mechanisms of interaction between EDs and charge carriers that lead to a narrowing or broadening of electroluminescence spectra and increase or decrease EQE, respectively. Both mechanisms involve multiphonon carrier capture and ionization, impacting EQE reduction and efficiency droop. The losses caused by these mechanisms directly affect EQE dependencies on current density and the maximum EQE values for LEDs, regardless of the emission wavelength. Another manifestation of these mechanisms is the reversibility of LED degradation. Recombination processes vary depending on whether QWs are within or outside the space charge region of the p-n junction.

Surface potentials in chemically etched n- and p-GaInP ₂ (100) are investigated by synchrotron-radiation photoemission spectroscopy at room and liquid-nitrogen temperatures. It is found that at low temperature the surface band bending in both n- and p-GaInP ₂ (100) is reduced so that the surface bands become nearly flat. This effect is explained in the framework of semiconductor surface electrostatics. The proposed model enables quantitative characterization of the surface state spectrum based on the experimentally determined values of the surface potential at different temperatures. In particular, the surface states density values obtained are 2 × 10 ¹² and 7 × 10 ¹² cm ^–2 for n- and p-GaInP ₂ (100) surfaces, respectively.

We provide the exact solution of the dispersion equation for a waveguided semiconductor structure with a photonic crystal core that provides the efficient second harmonic generation in the visible range. The comparison of the results with an approximate solution shows good agreement.