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The Modulation of Light by Non-Equilibrium Optical Phonons in n-Ge

✍ Scribed by L. E. Vorobev; V. I. Stafeev; A. V. Shturbin

Publisher
John Wiley and Sons
Year
1972
Tongue
English
Weight
491 KB
Volume
53
Category
Article
ISSN
0370-1972

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✦ Synopsis

Abstract

The modulation of light near the edge of the direct transitions in Ge in strong pulsed electric fields was investigated. High‐resistance n‐Ge (ϱ = 40 Ωcm) and low‐resistance p‐Ge (ϱ = 1.0 Ωcm) exhibit the Franz‐Keldysh effect only. The low‐resistance samples of n‐Ge (ϱ = 1.0 and 0.3 Ωcm) exhibit Franz‐Keldysh effect together with a variation of the absorption coefficient Δα~DE~ which is proportional to the free carrier concentration and has a threshold approximately at the photon energy deficit equal to the energy of the longwave optical phonon (0.037 eV). The additional absorption Δα~DE~ is caused by the indirect band‐to‐band transitions with participation of non‐equilibrium optical phonons, emitted by hot electrons. From a comparison of the experimental and calculated results for Δα~DE~ the lifetime is estimated to be 5 × 10^−11^ s at T~0~ = 90 °K for the long‐wave optical phonons. This value is in satisfactory agreement with Klemens' theory and also with the results of Raman scattering in Ge.

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