Amorphous pnictide semiconductor BaZn_2As_2 exhibiting high hole mobility

摘要

We selected BaZn_2As_2 as a candidate for a high-mobility p-type amorphous semiconductor because of the valence band maximum formed mainly of widely spread As 4p orbitals. The hole mobility of amorphous BaZn_2As_2 films increased from 1 to 10 cm~2 V~(-1) s~(-1) as the annealing temperature increased from 300 to 400 ℃. 500 ℃ annealing started crystallizing the film with the hole mobility ～20cm~2 V~(-1) s~(-1). The optical bandgaps of amorphous BaZn_2As_2 were 1.04-1.37 eV, which are much larger than that of the crystalline β-BaZn_2As_2 (0.23 eV). It is explained by the broken symmetry at the Ba site and the weakening of the As-As direct bonds, which is supported by 6 keV hard X-ray photoemission spectroscopy measurement.