Optical-absorption and Voigt-effect measurements in germanium have been performed in crossed electric and magnetic fields for photon energies just below the direct gap. The electric fields were taken between 2.8×${10}^4$ and 4.7×${10}^4$ V/cm, the magnetic fields were chosen between 62.5 and 96.5 kOe. Three transitions were observed, two of which are allowed for $E=0\mathrm{} (\Delta n=0)$, whereas the third is forbidden for $E=0\mathrm{}$, but is induced by the electric field ($\Delta n=-1\mathrm{}$). From the experimental data the energies of the three light-hole levels $|0a+〉$, $|1a+〉$, and $|0b+〉$ are deduced, under the assumption that the energies of the electron levels can be calculated according to the theory for a simple parabolic band in cross fields. A calculation is developed for the energies of the light-hole levels in cross fields for the range of high ($\frac{E}{H}$) values where a perturbation treatment is not sufficient. This calculation is within the framework of the effective-mass approximation and neglects the electric-field-induced coupling between light- and heavy-hole states. The theory shows that for higher ($\frac{E}{H}$) values the electric-field-induced shifts of the light-hole levels are comparable to those that would have been found in simple bands, and that the electric field removes the quantum effects in the energies of the light-hole levels. The theory is in satisfactory agreement with the experimental results.

Close

PrevNext

View figure in article