Abstract: | A short high-power pulse of ionizing radiation creates a high concentration of nonequilibrium electrons and holes in a dielectric.
They quickly lose their energy, generating a multiplicity of secondary quasiparticles: electron—hole pairs, excitons, plasmons,
phonons of all types, and others. When the kinetic energy of an electron becomes less that some value EΔ≈(1.3-2)Eg it loses the ability to perform collisional ionization and electron excitations of the dielectric medium. Such an electron
is said to be ionization-passive. It relaxes to the bottom of the lower conduction band by emitting phonons. Similarly a hole
becomes ionization-passive when it “floats up” above some level EH and loses the ability for Auger ionization of the dielectric medium. It continues to float upward to the ceiling of the upper
valance band only by emitting phonons. The concentrations of ionization-passive electrons and holes are larger by several
orders of magnitude than those of the active electrons and holes and consequently make of a far larger contribution to many
kinetic processes such as luminescence. Intraband and interband quantum transitions make the greatest contribution to the
fundamental (independent of impurities and intrinsic defects) electromagnetic radiation of ionization-passive electrons and
holes. Consequently the brightest types of purely fundamental luminescence of strongly nonequilibrium electrons and holes
are intraband and interband luminescence. These forms of luminescence, discovered relatively recently, carry valuable information
on the high-energy states of the electrons in the conduction band and of the holes in the valence band of a dielectric. Experimental
investigations of these types of luminescence were made, mainly on alkali halide crystals which were excited by nanoseconal
pulses of high-current-density electrons and by two-photon absorption of the ultraviolet harmonics of pulsed laser radiation
beams of nanosecond and picosecond duration. The present article gives the results of theoretical calculations of the spectra
and other characteristics of intraband electron and interband hole luminescence which are compared with the experimental data.
Institute of High-Current Electronics, Sibrian Branch of the Russian Academy of Sciences, Polytechnic University, Tomsk. Translated
from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 11, pp. 13–41, November, 1997. |