We present experimental results on continuous-wave generation of THz radiation by strained Ge and a theoretical model for population inversion of carriers giving rise to the stimulated THz emission. Resonant acceptor states induced by strain and resonance hole scattering under applied electric field are necessary for the inversion.
We report on the experimental evidence for terahertz (THz) lasing of boron-doped strained Si1−xGex quantum-well structures. The lasing arises under strong electric fields (300–1500 V/cm) applied parallel to interfaces. The spectrum of THz stimulated emission is presented showing the lasing wavelength near 100 μm and the modal structure caused by a resonator. The mechanism of population inversion is based on the formation of resonant acceptor states in strained SiGe layer.
Terahertz (THz) emissions corresponding to intracenter transitions of phosphorus impurities in silicon have been observed up to 30K. Electrical pulses (250ns) with a repetition rate of 413Hz were used for excitation, and the peak power was calculated to be ∼20μW∕facet for a 190×120μm2 device with a peak pumping current of 400mA at 12K. THz emission intensity increased linearly with pumping current and quenched when the sample temperature was above 30K. The current–voltage characteristics suggested a conduction and excitation mechanism by injection of electrons from a Schottky barrier followed by impact ionization of the neutral impurities.
We present a theoretical prediction of a new mechanism for carrier population
inversion in semiconductors under an applied electric field. The mechanism is
originated from a coherent capture-emission type inelastic scattering of
resonant states. We support our theory with concrete calculations for shallow
acceptor resonant states in strained p-Ge where a lasing in THz frequency
region has been recently observed.Comment: 4 pages, 3 figures submitted to Phys.Rev.Letter
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