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On the nature of E 1 ‐transitions in germanium
Author(s) -
Humlíček J.
Publication year - 1978
Publication title -
physica status solidi (b)
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.51
H-Index - 109
eISSN - 1521-3951
pISSN - 0370-1972
DOI - 10.1002/pssb.2220860135
Subject(s) - exciton , doping , impurity , electron , spectral line , germanium , electron density , saddle point , field (mathematics) , condensed matter physics , chemistry , materials science , molecular physics , physics , silicon , optoelectronics , geometry , organic chemistry , mathematics , quantum mechanics , astronomy , pure mathematics
The E 1 optical structure of Ge is studied by unmodulated, first‐derivative, and low‐field electroreflectance spectra. An extensive investigation of heavily doped samples shows only minor changes of their electron structure for impurity concentrations up to 6 × 10 19 cm −3 . As the freecarrier plasma screens the electron–hole interaction, exciton effects are reduced owing to the doping. While the exciton interaction is found to modify the electroreflectance lineshapes, its role is not essential in unmodulated and first‐derivative ones. The lineshape analysis of the room temperature spectra shows that the E 1 ‐structure is not well described by a simple parabolic critical point of the joint density of states, except for the low‐field electroreflectance, which is fitted satisfactorily by a two‐dimensional minimum (substituting a rather complex band structure with at least one M 1 saddle point).