金属間化合物ZnSnAs<SUB>2</SUB>単結晶の製作とその半導性

Abstract

Large single crystals of a semiconducting an intermetallic compound ZnSnAs2 have been grown by the Bridgman method. This compound crystallizes in either the chalcopyrite structure or the zinc-blende structure. The semiconducting properties of both structures have been studied. The resistivity, Hall coefficient, Seebeck coefficient and infrared absorption have been measured as a function of temperature. Measurements of the Seebeck coefficient and the infrared absorption were made only for the chalcopyrite structure. The results are as follows.Single crystals of ZnSnAs2 show p-type conductivity and cleave on the (110) plane. For single crystals having the chalcopyrite structure, a hole mobility of 130 cm2/V·sec and a carrier concentration of 1.2×1018/cm3 are observed at room temperature. The width of the forbidden energy gap for indirect transitions at 0°K of 0.59 eV is obtained from a slope of the intrinsic resistivity curve. The mobility ratios found by the usual procedure from the Hall coefficient maximum and determined from the resistivity data by the method derived by Hunter are 9 and 12, respectively. From the Seebeck coefficient data, the effective mass of holes is calculated to vary from 0.43 m0 at 296°K to 59 m0 at 557°K, and the relaxation time is found to be 2.6×10−14 sec at 296°K. The infrared absorption gives a value of 0.66 eV for the energy gap for direct transitions at room temperature and measurements over the temperature range from 88°K to 296°K suggest that the energy gap is about 0.74 eV at 0°K. For the disordered zinc-blende structure, a resistivity of the order of the 10−3 ohm-cm and a carrier concentration of the order of 1019/cm3 are shown at room temperature.