Figure 1

MPC spectroscopy data sets assuming homogeneous capture characteristics on amorphous Ge₂Sb₂Te₅ and Ag₄In₃Sb₆₇Te₂₆. MPC scans recorded at various temperatures are plotted as MPC DOS (see equation 4) against energy (with valence band edge E_V as reference, see equation 6), based on the assumption of c_p = const. for involved states. Data points that are identified as unaffected by the recombination zone are plotted bold, and the limits are marked by circles. The thin lines of the same color going beyond those circles represent data affected by the recombination zone, which are therefore ignored in the further analysis. Preliminarily scaling MPC scans with one common capture coefficient for holes (\({k}_{{\rm{c}}}{N}_{{E}_{{\rm{V}}}}=5\cdot {10}^{13}\,{{\rm{s}}}^{-{\rm{1}}}\,{{\rm{K}}}^{-1/2}\,{{\rm{eV}}}^{-{\rm{1}}}\)) yields a somewhat coherent MPC DOS in both materials. A continuous spectrum of localised states is observed, for which the MPC DOS appears to decrease exponentially from the valence band edge towards the bandgap center (see local fits). A slight curvature in MPC scans for Ge₂Sb₂Te₅ at elevated temperatures reveals the effect of a structural defect located at a specific energetic distance from the band edge. MPC scans for Ag₄In₃Sb₆₇Te₂₆ appear to be straight except from a flattening at elevated temperatures (T ≥ 150 K), which is most likely an artefact due to probing energy levels close to the Fermi level.