DIRECT GAP RECOMBINATION IN GERMANIUM AT HIGH EXCITATION-LEVEL AND LOW-TEMPERATURE

In highly excited germanium and at low temperatures, a luminescence is observed at energies above the indirect gap at an energy of 0.880 eV. This luminescence is generally observed in connection with a broadened electron-hole-drop emission line thus indicating an increased density in the plasma state. At the same time, absorption in that energy range is reduced drastically. This luminescence is attributed to direct recombination processes between the Γ2 conduction band minimum and the Γ25 valence band maximum. The measurements we report concern the dependence of this luminescence on excitation conditions keeping the bath temperature constant at 2K. Line-shape, line-width and energetic position indicate that free carrier band-to-band recombination and no excitonic effects are involved. The dependence of the luminescence intensity on excitation power is well explained by a coupling by Auger processes between the indirect and the direct gap in germanium. © 1978.