Growth and optical properties of Dy doped and undoped n-type InSe single crystal

Undoped n-InSe and Dy doped n-InSe (n-InSe:Dy) single crystals were grown b y a method which is similar to direct freezing method. Ingots had no cracks and voids on the surface. There were no processes to polish and clean trea tment at cleavage faces of these samples because of the natural mirror-like cleavage faces. The absorption measurements were carried out in n-InSe and n-InSe : Dy samples in the temperature range 10-320 K. The first exciton e nergies for n = 1 were calculated as 1.331, 1.248 eV in n-InSe and were 1.3 26, 1.244 eV in n-InSe:Dy at 10 and 300 K, respectively. The second exciton energies for n = 2 in n-InSe were calculated as 1.346, 1.336 eV and in n-I nSe : Dy were 1.340, 1.332 eV at 10 and 80 K, respectively. Binding energie s of n-InSe and n-InSe:Dy were calculated as 19.47 and 18.87 meV, respectiv ely. The direct bands gap for n-InSe are 1.350, 1.267 eV and for n-InSe : D y are 1.344, 1.263 eV at 10, 300 K, respectively. (C) 1999 Elsevier Science Ltd. All rights reserved.