抄録
Growth of amorphous ZnO by B doping and their opto-electrical properties are reported. The B-doped ZnO (ZnO:B) films were grown by pulsed laser deposition using polycrystalline ZnO:B ceramic targets. Although the solubility limit of B in bulk ZnO polycrystal was ~4%, 18%-doped ZnO:B showed the shrinkage in the c-axis length. Preferentially (002)-oriented polycrystalline ZnO:B films were grown for the B concentration [B] ≤ 18%; while, amorphous ZnO:B films were obtained for [B] ~26%. It was found that the density of the amorphous ZnO:B film was smaller by 9% than that of crystalline ZnO (5.61 g·cm−3), which is explained mainly by the incorporation of the light B atoms. The optical bandgap of the ZnO:B films increased with [B] and that of the amorphous ZnO:B film was ~3.38 eV. The amorphous ZnO:B films have low free electron density of ~1015 cm−3, suggesting the existence of electron traps. Hall mobility of the amorphous ZnO:B [~1 cm2(V·s)−1] was smaller than those of the polycrystalline ZnO:B films.
