In order to improve conversion efficiency of THz wave generation, Germanium (Ge)-doped gallium selenide (GaSe) single crystals have been grown by Temperature Difference Method under Controlled Vapor Pressure (TDM-CVP). In this article, electrical property and lattice constant of Ge doped GaSe ( GaSe: Ge) crystal are compared with that of not-intentionally doped GaSe crystal. Compared with non-doped GaSe crystal, carrier concentration p was decreased by Ge-doping (not-intentionally doped GaSe p = 3.2 x 10(15) cm (3) at 255 K, GaSe: Ge p = 4.9 x 10(14) cm (3) at 255 K). In addition, it has been confirmed that lattice constant of GaSe crystal increased with doping Ge concentration increased. (C) 2017 Elsevier B.V. All rights reserved.