Direct identification of the L′3 → L1 transition in Ge

Abstract
The electroreflectance (ER) spectra of n‐type Ge with free carrier concentrations of 6.2 × 1018 cm−3 are studied within the energy range of the E1 and E1 + ΔI transitions. A detailed analysis of the spectra shows in addition to the Franz‐Keldysh (FK) effect an electron distribution (ED) effect, too. An appropriate electrode potential decreases the intensity of the electric field and increases the probability of the occupation of the bottom of the conduction band at the same time so that the ED effect predominates over the FK effect in the ER spectrum. The lineshapes of both the effects agree well with the theoretical curves. Therefore the transition L′3 → L1 clearly manifests itself in the E1, E1 + δ1 structure.