A new semiconducting ferroelectric [Ga_1-xGe_xTe]

Abstract

The dielectric properties of a new semiconducting alloy Ga_1-xGe_xTe (x=0.10 - 0.49) have been studied and found to show ferroelectric behavior. The crystal structure was found to be GaTe-like (monoclinic) upto x = 0.10 and changed to GeTe-like (rhombohedral) from x = 0.25. The dielectric constants (ε _c and ε ⊥_c) at 300K increased monotonically with x reaching 255 and 360 respectively at x = 0.49. The Curie temperature T_c decreased from 497° C for x = 0.10 to 428°C for x = 0.49, the transition being shown to be of second order. Ferroelectric behavior was confirmed by well - defined hysteresis curves, the spontaneous polarisation (P_s) being 5.75 μ C/cm² and the coercive field (E_c) 85 kV/cm at 300K for x = 0.35. The band-gap of the alloy decreased from 1.66 eV for x = 0 to 0.62 eV for x = 0.49 indicating its semiconducting nature, the highest resistivity of 105 Ω-cm being obtained in the layer plane for x = 0.10.