Effect of Pressure on the Amorphous Ge-Chalcogenide Materials

The effects of the hydrostatic pressure on the optical gap Eg of the amorphous Ge-chalcogenide semiconductors are reviewed. The absorption edge Eg shifts largely to low frequency side and the parameter Γ of the Urbach tail increases with the increase of the pressure. For the composition near GeS2, sudden anomalous changes of Eg and also Γ are observed in the pressure range of 2∼4 GPa. These anomalous effects are considered to originate from the change of the internal structure. Raman spectra exhibit interesting large change under the pressure especially in the low frequency region, and the characteristic properties of the Raman spectra of the amorphous Ge-chalcogenide semiconductors are also reviewed.