Electrical transport properties of p-GaTe grown by directional freezing method

p-type GaTe single crystals have been grown using the directional freezing method with different growth rates. Temperature-dependent Hall effect and resistivity measurements were carried out in the 80-325 K temperature range and at 1.6 T magnetic field. The free carrier concentration in the exhaust region was in the range of 9 x 10(15)-8 x 10(16) cm(-3) for growth rates of 3.3-0.39 mum s(-1) and the hole mobility at 300 K ranged from 4.8 to 21 cm(2) V-1 s(-1). A systematic dependence of the hole carrier concentration and room temperature hole mobility on the growth rate was not observed. From temperature-dependent Hall measurements, we have found that the compensation ratio N-D/N-A was in the range of 0.39-0.69 regardless of the growth rate. The highest mobility of 342 cm(2) V-1 s(-1) at 100 K was achieved after annealing at 200 degreesC for 30 min. The fitting of the temperature-dependent free carrier concentration, using the single acceptor-single donor model, was used to determine the compensation ratio. Finding N-max(m*)(3/2) = 3.15 indicates high effective mass for holes or the possibility of a few close maxima of valence band edges with different effective masses.