Optical Constants of Germanium in Spectral Region from 0.5 eV to 3.0 eV

Abstract

The optical constants for electropolished intrinsic germanium have been determined for the spectral region between 0.5 and 3.0 eV at 300 and 120°K. The technique is based on the determination of the ratio ${\mathcal{R}}_n=\frac{R_{\mathrm{II}}}{R_{\perp }}$ at its minimum value and the precise measure of the pseudo-Brewster angle ${\varphi }_B$ at that minimum, after correction for the presence of an oxide layer. Six distinct spectral features are observed, 4 of which have been reported by other investigators. These 4 consist of the two doublets, one at the $\Gamma$ point, the other at $\Lambda$, each with the spin-orbit splitting effect. The other features, at 1.74 and 1.94 eV (300°K), and 1.84 and 2.04 eV (120°K), are attributed to direct transitions $L_{3^{\prime }}-L_1$. A discussion of the optical constants in terms of the joint density of states is also given. A comparison is made between normal reflectance values as calculated from the optical constants and recent very precise experimental normal reflectance measurements.