Low Temperature Photoluminescence Properties of Silicon and Silicon-Germanium Alloys
<p>In this thesis, three examples of the application of the photoluminescence technique to indirect semiconductors at low temperatures are presented.</p> <p>Chapter 2 deals with the effect of increasing impurity concentrations on the photoluminescence spectrum. We present result...
| Summary: | <p>In this thesis, three examples of the application of the photoluminescence technique to indirect semiconductors at low temperatures are presented.</p>
<p>Chapter 2 deals with the effect of increasing impurity concentrations on the photoluminescence spectrum. We present results for the Si:(B,In) system. As the In concentration is increased, we observe quenching of B luminescence. We propose a model based on exciton transfer from B to In impurities, which agrees well with the experimental results when the exchange mechanism is assumed for the transfer. This is the first observation of exciton transfer in Si.</p>
<p>Chapter 3 deals with the properties of three sharp and relatively intense features in the photoluminescence spectrum of Si:In. We observe these lines, which are labelled "P,Q,R", only in the luminescence of Si:In. We present measurements of the lifetimes of P,Q,R luminescence which show that these lines have extremely long lifetimes. These results suggest that the P,Q,R lines are associated with an isoelectronic complex in Si. We present measurements of the temperature dependence of P,Q,R luminescence and P,Q,R lifetimes which support this conclusion. This is the first observation of luminescence associated with an isoelectronic complex in Si. In addition, we present results which show that the P,Q,R luminescence intensities are very sensitive to the sample surface preparation. This is the first observation of surface sensitive photoluminescence.</p>
<p>Chapter 4 deals with the photoluminescence properties of undoped and In doped Si-rich Si-Ge alloys. We identify the alloy luminescence features on the basis of the temperature dependence, time dependence and pump power dependence of the luminescence intensities. We present results for the band gap shift and free exciton binding energy for each sample examined. In addition, we present a model for the observed broadening of bound exciton luminescence. Finally, we present observations which suggest that excitons bind to local fluctuations in alloy composition at low temperatures. This is the first investigation of the photoluminescence properties of Si-rich Si-Ge alloy semiconductors.</p> |
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