E. G. Chirkova

Resonant acceptor states and terahertz stimulated emission of uniaxially strained germanium

The stimulated emission spectrum of uniaxially strained p-Ge is presented. The energy spectrum of the states of a shallow acceptor in Ge under uniaxial compression is calculated. The threshold pressure at which the acceptor state split off from the ground state becomes resonant is found. The pressure dependence of the width of this resonant level is calculated. The stimulated emission lines are identified. In particular, it is shown that the principal emission peak corresponds to the transition of holes from the resonant 1s (1sr) state to the local p±1 state. The probabilities of optical transitions are calculated. A mechanism of population inversion due to the intense resonant scattering of hot holes with an energy corresponding to the position of the 1sr level is proposed.

Stimulated THz emission of acceptor-doped SiGe/Si

An intense THz emission was observed from strained SiGe/Si quantum-well structures under strong pulsed electric field. The p-type structures were MBE-grown on n-type Si substrate and δ-doped with boron. Lines with wavelengths near 100 microns were observed in the emission spectrum. The modal structure in the spectrum gave evidence for the stimulated nature of the emission. The origin of the THz emission was attributed to intracenter optical transitions between resonant and localized boron levels.

Far-infrared lasing due to intracenter optical transitions in Ge

Stimulated emission of far-IR radiation from uniaxially compressed p-Ge in strong electric fields is shown to be due to population inversion of strain split acceptor levels. The peak corresponding to the optical transitions between split- off and ground acceptor states is found in the spectrum of stimulated emission. The strong frequency tuning by stress due to pressure dependence of the energy splitting of these states is obtained. The inversion takes place as the split- off acceptor state is in the valence band continuum.

Induced Radiative Transitions between Strain-Split Acceptor Levels in Germanium at Strong Electric Field

Earlier we have observed the induced far-infrared emission from uniaxially compressed p-Ge at strong electric field but with no magnetic field [1]. The possible reason for the induced emission was shown to be a population inversion of strain-split shallow acceptor levels [2]. In this report we present the first spectral investigations of the induced radiation carried out by means of far-infrared grating monochromator. The data obtained show that the induced emission in compressed p-Ge is due to the radiative transitions between strain-split impurity levels when the one of them lies in a continuous band spectrum.