The infra-red absorption of hot semiconducting diamonds

Abstract

Measurements of the absorption of p-type semiconducting diamonds have been made at temperatures in the range 450 to 600°k and over the wavelength range between 6 and 45 μ. The major effect observed is an absorption, which is present only in hot semiconducting diamonds, which increases with increasing wavelength and temperature. The increase with temperature is similar to that of the increase in carrier concentration as determined from measurements of the Hall effect. The observed wavelength dependence differs from that predicted by the theory of intervalence band absorption for mass ratios of 1·04, 1·25, 2·5 and 5. It is possible to account for the shape of the spectrum using the single band free carrier theory of Donovan and March. However, the relaxation times deduced are small (c. 10⁻¹⁴ sec at 563°k) and there is a discrepancy between the calculated and observed magnitude of absorption.