Auger recombination of electron-hole drops

Phonon-assisted Auger recombination is calculated for indirect band gap semiconductors in the strongly degenerate case. It follows a reciprocal lifetime τ^?1=Cn² with C=7.19×10³¹ cm⁶ sec^?1 for Si and C=2.94× 10^?31 cm⁶ sec^?1 for Ge. These results are in good agreement with experimental values of the decay of electron-hole drops. Therefore one can conclude that phonon-assisted Auger recombination is the essential nonradiative recombination process in this case.     

Non-radiative recombination of electron-hole drops by means of phonon-assisted Auger recombination

Phonon-assisted Auger recombination is shown to be the essential non-radiative recombination process of electron-hole drops. The calculation gives a reciprocal lifetime τ^-1 = Cn², where the coefficients C are in satisfactory agreement with experimental values. This is shown for Ge, Si and GaP.     

Evidence for high temperature electron-hole droplets in heavily doped silicon

The photoluminescence spectrum of silicon containing 2.0 × 10¹⁸ phosphorous atoms/cm³ is studied as a function of temperature in the range 1.5 K?T?80 K. A threshold temperature is not observed for the electron-hole droplet photoluminescence line. The results indicate that the impurity band becomes unstable with increasing temperature and disappears abruptly at about 51 K.     

Phonon-assisted radiative electron-hole recombination in silicon quantum dots

The temperature dependence of the photoluminescence (PL) spectrum of silicon quantum dots (QDs) is studied both theoretically and experimentally, and the time of the corresponding electron-hole radiative recombination is calculated. The dependence of the recombination time on the QD size is discussed. The experiment shows that the PL intensity decreases by approximately 60% as the temperature increases from 77 to 293 K. The calculated characteristic recombination time has only a weak temperature dependence; therefore, the decrease in the PL intensity is associated primarily with nonradiative transitions. It is also shown that the phonon-assisted radiation is much more efficient than the zero-phonon emission. Moreover, the zero-phonon recombination time depends on the QD radius R as R⁸, whereas the phonon-assisted recombination time depends on this radius as R³.     

Nucleation of electron-hole droplets at swirl defects in silicon

Electron-hole droplets (EHDs) are revealed to be formed more preferentially in the defective area than in the defect-free area in silicon with swirl defects. That is, lattice defects which cause swirl defects act as nucleation centers of droplets more effectively than shallow-level impurity atoms. Luminescence intensity profile of droplets on the sample surface is found to correspond well to the swirl pattern and EHD and bound exciton peak intensities are rather competitive, while luminescence intensity due to free excitons is almost homogeneous in the sample.     

Phase diagram for electron-hole droplets

The phase diagram for electron-hole droplets is obtained using a phenomenological spin one lattice gas model treated in mean field approximation. Very good agreement with experimental data can be obtained.     

Hydrodynamic model for electron-hole droplets

The hydrodynamic equations of change are combined with the density functional formalism. This provides a model for critical and stable electron hole droplets which is applicable throughout the phase diagram.     

Nonradiative electron-hole recombination by a low-barrier pathway in hydrogenated silicon semiconductors

A microscopic pathway for nonradiative electron-hole recombination by large structural reconfiguration in hydrogenated Si is found with first-principles calculations. Trapped-biexciton formation leads to a low-barrier reconfiguration of the H atom, accompanied by crossing of doubly occupied electron and hole levels in the band gap. This crossing represents the nonradiative recombination of the carriers, without multiphonon emission. The proposal provides a mechanism for carrier-induced H emission during metastable degradation of hydrogenated amorphous silicon.     

Surface properties of electron-hole droplets in semiconductors

The leading gradient terms in the kinetic energy densities of the electrons and holes in Ge and Si type semiconductors are calculated including band structure effects. Band structure effects are found to increase these gradient terms substantially over those for isotropic bands. The surface properties of electron—hole drops in Ge are studied using these gradient terms with several local energy densities, and band structure effects in the gradient terms are shown to increase the surface thickness, surface energy and dipole barrier over isotropic band results. The difference in the chemical potentials of the electrons and holes obtained from these approximate energy functionals indicates that the drop becomes positively charged, which is opposite in sign to that proposed recently by Rice.     

Critical point for electron-hole droplets in strained Ge and Si

For Ge and Si under a high uniaxial stress, the split valence bands become non-parabolic. The effect of the non-parabolicity on the critical point of the electron-hole droplet in Ge(111) and Si(100) is investigated. The ground state properties of the droplet are also calculated.     

Alloy-assisted Auger recombination in InGaN

It has been numerically investigated the effect of alloying on the Auger recombination rate in wurtzite type n-InGaN. In order to explicitly take into account the effect of alloy disorder, the calculations have been performed with a 256-atom supercell that includes In and Ga atoms randomly distributed over the supercell sites to obtain a given composition. A full band structure (no band scissors-shifting) and high-dense inhomogeneous k-point grid were used to improve the accuracy of the calculations. We show that the large number of allowed interband Auger transitions originated by the breaking of the translational periodicity plays a crucial role in the wide band gap InGaN alloys. The alloy-assisted Auger coefficients for these alloys are in the 1.0?×?10^?32–4.7?×?10^?31 cm⁶/s range     

Mutual influence of Auger and non-radiative recombination processes under silicon femtosecond laser irradiation

The results of theoretical study of the contribution of recombination processes in additional heating of the surface of monocrystalline silicon during multipulse femtosecond laser processing are presented to discussion. The numerical evaluations are made in regimes of the laser radiation below the ablation threshold, when the microgeometry of the surface is formed due to the processes of self-organization. The influence of Auger recombination processes on the photoexcitation of the semiconductor during the pulse and relaxation after the pulse is studied in detail. It is shown that the additional heating of the surface due to non-radiative recombination is extremely small at pulse repetition rate 10 Hz–1 MHz. Mutual influence of recombination processes of both types is shown.     

Radius of electron-hole drops in silicon

The radius of electron-hole drops at nucleation threshold is investigated as a function of temperature in Si using a small shift of their main luminescence line due to their surface energy. For T > 10 K, experiment and theory are consistent if we take into account a sticking coefficient (～ 4%) at the drop surface. For T ? 10 K our data indicate that the drop size is certainly small, but the measured radii are not likely. This suggests that other effects should be considered, such as the drop curvature energy for example.     

Auger recombination in diamond-like narrow-gap semiconductors

In the calculation of the transition rate of Auger recombination in the Kane model the overlap integral between the wave functions of the conduction and heavy hole bands is equal to zero at the threshold. As a result the preexponential function has a different temperature dependence in comparison with the case of simple parabolic bands. The theoretical value of the recombination lifetime is in agreement with experimental data for InSb at 300 K. Estimates of the overlap integral given earlier are analyzed.     

Selection rules for bound exciton Auger recombination in semiconductors

We use selection rules developed for Auger-electron spectroscopy to study non-radiative transitions of neutral acceptor bound excitons. We show that (total) angular momentum selection rule implies that excitons originating from the J = 0 and the J = 2 two-hole states have different Auger transition probabilities. The results are shown to be in agreement with photoluminescence experiments.