Absorption of Light in Se near the Band Edge

Abstract

A photovoltaic method has been used to measure the relative absorption in hexagonal Se of photons of energy 1.6 ev to 2.0 ev in the temperature range 80°K to 440°K. The measurements show that the transitions are indirect at the band edge, requiring the absorption or emission of a phonon. The energy gap is found to be (1.79±0.01) ev at 300°K; above this temperature $\frac{d{E}_G}{\mathrm{dT}}=-9\mathrm{}\times {10}^{-4\mathrm{}}$ ev/degree. The absorption edge of hexagonal Se is compared with that of amorphous Se.