Composite Zn_1-x Cd _x GeAs₂ semiconductors: structural and electrical properties

We present the studies of structural, transport and magnetotransport properties of [Formula: see text]Cd _x GeAs₂ crystals with the chemical content changing from 0 to 1. The structural studies indicate that this alloy exists as a composite two-phase material in almost the entire range of average chemical compositions. The two phase nature of our samples does have a significant influence on the carrier transport and magnetotransport of the composite alloy. The change of the conductivity type is observed at room temperature, from p-type for [Formula: see text] to n-type for x  >  0.18, respectively. The Hall carrier mobility measured at room temperature decreases as a function of x from about 35 cm² (V · s)^-1 for the sample with x  =  0 down to 3 cm² (V · s)^-1 for the sample with x  =  0.233. For x  >  0.233 the Hall carrier mobility shows an increase with x, up to the highest value around 875 cm² (V · s)^-1 observed for the sample with x  =  1. Temperature dependent resistivity measurements indicate the presence of thermal activation of carriers with activation energy, E _a, with values from 20 to 30 meV for all the studied samples. The temperature dependent Hall effect data show that the grain boundary limited transport is strong in all our samples. For the samples with [Formula: see text] the negative MR is observed at temperatures lower than 100 K and at low magnetic field values, [Formula: see text] T. This effect is interpreted as a weak localization phenomenon with low values of phase coherence length, [Formula: see text] nm.