W. Schmid

Excitons bound to an isoelectronic trap in silicon

Abstract Three novel emission lines in silicon. A, B, and C, are reported which are associated with an exciton bound to an isoelectronic trap. We deduce this interpretation from temperature dependent measurements as well as from Zeeman-, piezo-, and time-resolved spectroscopy. The binding center is assumed to involve carbon.

Formation and decay of electron-hole drops in Si

Abstract Using a single photon counting technique we were able to measure with very high time resolution the rise and decay times of the luminescence of free excitons and electron hole drops in Si. It was found that the formation and decay of droplets can be described by kinetic equations. The experimental data concerning the time behavior of the free excitons cannot be described by analogous simple kinetic equations. Therefore it is concluded that droplets are formed directly from a dense plasma rather than from a free exciton gas.

Indium bound exciton luminescence in silicon

Abstract A high-resolution photoluminescence study is presented of the bound exciton line and its 4 meV low energy satellite in Si:In. The excitation and temperature dependence and the decay times suggest that the satellite line originates from the decay of an exciton bound to the indium acceptor. We tentatively correlate this line with excitations of the final state indium acceptors into a vibrational excited level.

Donor-acceptor pair spectra in Si: In LPE-layers

Abstract We have grown In-doped silicon layers by liquid phase epitaxy. Samples grown with a small cooling rate display a large number of sharp lines in the low temperature photoluminescence spectra which can be interpreted as donor-acceptor pair transitions between the donor P and the acceptor In. At lower energies a broad band originating from distant pairs is observed. Samples grown with higher cooling rates exhibit only bound-exciton and intrinsic luminescence.

Impurity-assisted intervalley scattering in uniaxially stressed silicon

Abstract F-type intervalley scattering in stressed silicon is studied by means of photoluminescence from “hot” and “cold” electron-hole drops and free excitons. The scattering rates are shown to be essentially determined by the impurity concentration before TA-phonons initiate complete thermalization among the electrons in the up- and down-shifted conduction valleys. For phosphorus donors, scattering probabilities of ⋍ 2x10 −6 cm 3 sec are obtained. Much lower scattering probabilities are found for boron acceptors.

Experimental evidence against the shell model of bound multiexciton complexes in silicon

Abstract We report time resolved and piezospectroscopic measurements on the bound exciton low energy satellite line series induced by the donor phosphorus in silicon. This line series was recently interpreted in terms of a multiple exciton model arranging electrons and holes in shell states around the neutral impurity. Our experimental data are in significant contradiction to a number of properties predicted by this model. We believe that the shell model has therefore to be discarded as a means of the lines interpretation.

Stress dependent kinetics of electron-hole drops in uniaxially deformed silicon

Abstract The decay of electron-hole drops in silicon is studied as a function of uniaxial stress applied along the and crystallographic directions. For stress, the decay kinetics can be explained in terms of Auger recombination. In contrast, for stress, the experimental decay is consistent with a model of free exciton evaporation from droplets rather than Auger recombination.