A NEW SEMICONDUCTING FERROELECTRIC [GA1-XGEXTE]

The dielectric properties of a new semiconducting alloy Ga1-xGexTe (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 (epsilon(parallel-to c) and epsilon(perpendicular-to c)) at 300K increased monotonically with x reaching 255 and 360 respectively at x = 0.49. The Curie temperature T(c) decreased from 497-degrees-C for x = 0.10 to 428-degrees-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 muC/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 10(5) OMEGA-cm being obtained in the layer plane for x = 0.10.