The spectrum of spontaneous terahertz electroluminescence was obtained near the breakdown threshold of a shallow acceptor (Ga) in germanium. The emission spectra were recorded by the Fourier spectroscopy method at a temperature of ∼5.5–5.6 K. The emission spectrum exhibits narrow lines with maxima at ∼1.99 THz (8.2 meV) and ∼2.36 THz (9.7 meV), corresponding to the optical transitions of nonequilibrium holes from the excited impurity states to the ground state of impurity center. A broad line with a maximum at ∼3.15 THz (13 meV) corresponding to the hole transitions from the valence band to the impurity ground state is also seen in the spectrum. The contribution of the hole transitions from the states of the valence band increases upon an increase in the electric-field strength. Simultaneously, the optical transitions of nonequilibrium holes between the subbands of the valence band appear in the emission spectrum. The integral terahertz-emission power is ∼17 nW per 1 W of the input power.

The observation of intense terahertz luminescence under the interband photoexcitation of n-GaAs and p-Ge semiconductors at low temperatures is reported. The terahertz photoluminescence is caused by radiative transitions, which accompany the capture of nonequilibrium carriers by impurity centers. These centers are in turn created in the crystal due to the impurity-assisted electron-hole recombination. The external quantum yield of the luminescence reaches 0.1%.

We report on efficient terahertz emission in the region of 1.5-2 THz from high electric field biased 6H-SiC structures with a natural superlattice (NSL) at liquid helium temperatures. The shape of the THz emission spectrum, the linear dependence of its maximum on the bias, the characteristic field strength required to achieve the emission, and the linear polarization of the emission along the natural superlattice axis allow it to be attributed to steady-state Bloch oscillations of electrons in the 6H-SiC natural superlattice.

The experimental observation and study of terahertz photoluminescence upon the steady-state interband excitation of epitaxial n-GaN(Si) layers are reported. The properties of the terahertz emission spectrum and the dependence of the spectrum on temperature and photoexcitation intensity suggest that emission occurs due to the trapping of nonequilibrium electrons at charged donors. In the n-type material at low temperatures, charged donors can be formed as a result of the recombination of nonequilibrium holes with electrons localized at donor centers. The main contribution to terahertz photoluminescence is made by 2P → 1S optical transitions between the first excited state and ground state of the donors. In addition, optical transitions of electrons from the conduction band states to the ground state as well as to the excited states of donors are evident in the terahertz emission spectrum.

Films of CH3NH3PbI3 organometallic perovskite, which is currently considered as a promising basic material for new-generation solar cells, as well as films containing CsPbI3inorganic lead–halid...