Photoluminescence in germanium with a quasi-equilibrium dislocation structure

The dislocation-related photoluminescence of n-Ge single crystals with a quasi-equilibrium structure of 60 degrees dislocations is investigated at a temperature of 4.2 K. It is shown that the dislocation-related photoluminescence spectra arc described by a set involving from 8 to 13 Gaussian lines with a width of less than 15 meV. With due regard for the data available in the li terature, the Gaussian lines with maxima at eneraies in the range 0.47 < E-m <= 0.55 eV are assigned to the emission of 90 degrees Shockley partial dislocations involved in quasi-equilibrium segments of 60 degrees dislocations with different values of the stacking fault width Delta (Delta = Delta(0), Delta < Delta(0), and Delta > Delta(0)). It is revealed that the d8 line at the energy E-m = 0.513 eV, which corresponds to the emission of straight segments with the equilibrium stacking fault width Delta(0), dominates in the photoluminescence spectra only at dislocation densities N-D < 10(6) cm(-2). As the dislocation density N-D increases, the intensity of the d8 line decreases with the d7 line (E-m approximate to 0.507 eV) initially and the d7 and d6 lines (E-m approximate to 0.501 eV) then becoming dominant in the photoluminescence spectrum. The d7 and d6 lines are attributed to the emission of segments with stacking fault widths Delta < Delta(0). Possible factors responsible for the formation of stacking faults with particular widths A Delta(0) for quasi-equilibrium dislocations are discussed.