Electro- and photoluminescence spectra of high-brightness light-emitting AlGaN/InGaN/GaN single-quantum-well structures are studied over a broad range of temperatures and pumping levels. Blue shift of the spectral peak position was observed along with an increase of temperature and current. An involvement of band-tail states in the radiative recombination was considered, and a quantitative description of the blue temperature-induced shift was proposed assuming a Gaussian shape of the band tail.

Electrical and optical properties of Nichia double-heterostructure blue light-emitting diodes, with In 0.06 Ga 0.94 N:Zn, Si active layer, are investigated over a wide temperature range from 10 to 300 K. Current-voltage characteristics have complex character and suggest the involvement of various tunneling mechanisms. At small voltages ͑and currents͒, the peak wavelength of the optical emission shifts with the applied bias across a large spectral range from 539 nm ͑2.3 eV͒ up to 443 nm ͑2.8 eV͒. Light emission takes place even at the lowest temperatures, indicating that a complete carrier freeze-out does not occur.

Semiconductor ultralow-threshold InAs quantum-dot lasers are investigated operating at 1230–1250 nm at room temperature (laser threshold range is of 16–83 A/cm2 for ground-state emission). The dependence of gain on current is derived from measurements of the threshold current as a function of the cavity length. The ground-state gain appears at very low current: the inversion threshold of ∼13 A/cm2 is a record low value. Analysis of these data for diodes of different molecular beam epitaxial-grown wafers leads to a squared dipole moment of the transition of ∼9.2×10−57 C2 m2 that corresponds to the length of elementary dipole of ∼0.6 nm.

In connection with some spectral anomalies of the luminescence in III–V semiconductors, we consider here the red spectral shift in partially disordered semiconductors, namely, in heavily doped GaAs and in alloys of InGaP and InGaN. The shift (of the Stokes type) between the Gaussian absorption peak and the quasi-equilibrium low-intensity luminescence peak is equal to σ2/kT, where σ2 is the dispersion of the Gaussian. As this shift is strongly temperature dependent, the temperature-induced blueshift anomaly appears in the temperature dependence of the luminescence peak position in III–V materials. The broadening parameter σ can be derived from spectral measurements. It is determined by the Coulomb-related fluctuations in heavily doped materials or by composition variations in disordered alloys (in bulk materials). In nanostructured materials additional factor of the disordering appears due to roughness of interfaces.