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Effects of the growth temperature and As/Ga flux ratio on the incorporation of excess As into low temperature grown GaAs

In previous studies we have investigated artefacts which appear in analysed parameters of positron lifetime spectra containing distributed o‐Ps lifetimes. Recently, we discovered also that the disagreements between the experimental positronium lifetime parameters and theoretical expectations, I1/I3 > Ip‐Ps/Io‐Ps = 1/3 and τ1 > τp‐Ps, may be well understood by assuming a distribution of e+ lifetimes in addition to an o‐Ps lifetime distribution. In this paper we give further experimental evidence for these deviations by taking positron lifetime spectra of high statistical accuracy for various amorphous polymers. Furthermore, a systematic study of the influence of the widths of the e+ and o‐Ps lifetime distributions on the analysed lifetime parameters will be presented. The analysis of computer‐generated spectra showed that all of the analysed lifetimes τ1, τ2 and τ3 increase artificially with increasing width of the e+ and o‐Ps lifetime distributions. The intensity I1 increases also, while I2 and I3 decrease. The deviations of I1/I3 and τ1 from the theoretical expectations are mainly controlled by the width of the e+ lifetime distribution. Suggestions for suitable constraints in the discrete‐term analysis in order to get reliable lifetime parameters are also made.

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