Oscillatory Spectral Distribution of the Photoelectromagnetic Effect Associated with Direct Interband Transitions in Germanium

Abstract

A rather simple and straightforward experimental method of studying direct interband optical transitions between Landau levels in semiconductors is achieved by observing the oscillatory spectral distribution of the photoelectromagnetic effect resulting from a quantizing magnetic field. The method is applied here to germanium at a temperature of 6 K, over the energy range 0.9–1.1 eV, using linearly polarized light parallel and perpendicular to magnetic fields of up to 70 kG applied along the [111] direction of the crystals. The spectral oscillations are analyzed in terms of current magneto-optical theories to give a value for the direct band-gap energy (Eg = 0.888 ± 0.001 eV) for the ground state exciton binding energy (Eex = 1.5 ± 0.3 meV) and an estimate of nonparabolicity and excitonic effects on higher-order transitions. A possible relationship between the oscillation amplitude and the bulk mean free path of the carriers is also examined.