Bonds and band structure inGexSe1−xcompounds

Abstract

The electronic structure of ${\mathrm{Ge}}_x{\mathrm{Se}}_{1-x}$ compounds is studied in a tight-binding approximation for $0\le x\le \frac{1}{3}$. The starting point consists of a "molecular approximation." The widening of the molecular levels into bands is then analyzed. The band gaps are shown to depend only on the local order. Qualitative results about the $s$ or $p$ character of the different bands are derived. It is shown that the behavior of optical properties with respect to $x$ is correctly predicted. Essential features that one should observe in photoemission spectra are also described.