Thermoelectric properties and nonstoichiometry of GaGeTe

► We explore thermoelectric and transport properties of Ga1+xGe1−xTe and GaGeTe1−y. ► GaGeTe is p-type degenerate semiconductor; the hole concentration increase with x and y. ► Maximum power factor σS2=3.6×10−4 Wm−1 K−2 at 475 K.