Determination of Free Exciton Capture Cross Section of Si:Al by Photoluminescence

Abstract

The free excitons capture rate and capture cross-section of the neutral A1 atom in silicon were determined at 4. The FE capture rate (c0) of Αl is evaluated from the changes of the relative intensities of photoluminescence (PL) spectra as a function of excitation density according to [4]. Two samples with different concentrations of Al (ΝΑΙ) were measured. In Fig. 1 the PL spectum of the higher doped sample is shown. The analysis, with the help of calibration curves, yields ΝΑ1 = 5.3 x 10 14 cm-3 and NΑ1 = 1.4 x 10 ί3 cm-3 for the two samples. The capture rate c 0 is calculated according to where vth is the average thermal velocity of FE, R0b/f(q, q') is the ratio of the peak heights of bound exciton (BE) and FE-related luminescence for diminishing excitation density, q and q' are the participating phonons in recombination and Wb/f(q, q') denotes, the ratio of radiative transition rates of BE relative to FE. The nonradiative Auger transition rate of an exciton bound to Al (τ = 76 ns) was taken from [7]. To calculate Wb/f(NP,TO) one needs the intrinsic full width at half maximum (FWHM) of the corresponding peaks. These values are sample-dependent and have to be evaluated. FWHM of the AlNP(J = 0) peak (869)