Influence of hydrogen treatment of CdTe crystals on the reflectivity spectra

Abstract The measurements of the reflection coefficient of the strongly hydrogenated CdTe crystals with various hydrogen contents have been performed in the wavelength range 190÷1400 nm. Two different types of integrating spheres (the Ulbricht balls) and an automatic double-beam reflectometer have been used for optical measurements. The maxima related to the interband transitions at the centre of the Brillouin zone ( E 0 transitions), at Λ critical points ( E 1 , E 1 + Δ 1 transitions) and in the volume of the Brillouin zone ( E 2 ) have been observed. A high-intensity, wide reflectivity maximum appears at 966 nm, i.e. for the photon energy (1.28 eV) smaller than the energy gap. The height of this maximum depends on the hydrogen content in the CdTe crystals. The differences observed in the fundamental reflectivity spectra are coherent with the results of atomic force microscopy (AFM) measurements. The experimental results indicate considerable influence of strong hydrogenation on the process of crystallization of CdTe from the vapour.