Growth and temperature dependence of optical properties of Er doped and undoped n-type InSe

n-InSe and Er doped n-InSe (n-InSe:Er) single crystals were grown by the mo dified Bridgman-Stockbarger method. The prepared InSe and InSe:Er single cr ystal ingots were 12 mm in diameter and about 80 mm in length. The ingots h ad no cracks or voids on the surface. The absorption measurements were carr ied out for n-InSe, and n-InSe:Er samples in the temperature range of 10-32 0 K. Binding energies of n-InSe and n-InSe:Er were calculated to be 20.5 me V and 21.0 meV respectively. The direct band gaps were estimated to be 1.33 9 eV, 1.289 eV and 1.256 eV in n-InSe and were 1.338 eV, 1.288 eV and 1.253 eV in n-InSe:Er at 10 K, 200 K and 300 K, respectively. E-o (1.247 eV) obt ained from the Urbach rule is nearly equal to the energy gap of n-InSe at 3 00 K.