HALL-MOBILITY AND CONDUCTIVITY IN ZNXCD1-XS MIXED-CRYSTALS

The electrical conductivity and Hall mobility of mixed crystals of Znxd1-x)S have been measured from 95 to 300 K for a range of compositions with 0 ≤ x ≤ 0.45. Crystals were grown from the vapour phase over the full range of composition and were found to have the hexagonal wurtzite structure for 0 < x > 0.85. Lattice parameters and the forbidden bandgap were found to follow Vegard's law very closely. Crystals with x > 0.45 were semi-insulating and were unsuitable for electrical measurements. Crystals with 0 < x < 0.15 were essentially similar to CdS. There was only a relatively small reduction in the room temperature values of mobility and conductivity from 300 cm2 V-1 s-1 and 10 Ω-1 cm-1 at x = 0 to 235 cm2 V-1 s-1 and 1 Ω-1 cm-1 at x = 0.15. The mobility could be described as limited by a combination of polar optical, piezoelectric and ionized impurity scattering. With increasing zinc concentration beyond x = 0.15 the mobility collapsed dramatically, although the free electron concentration remained in the vicinity of 1017 cm-3 at least up to x = 0.45. For example mobilities were of the order of 5 cm2 V-1 s-1 at x = 0.25. The mobility of this compositional range decreased with decreasing temperature as T 3 2 suggesting that ionised impurity scattering was now dominant. Other possible mechanisms, such as alloy and space charge scattering were also considered. © 1989.