Bulk crystal growth and characterization of ZnSnP₂ compound semiconductor by flux method

ZnSnP 2 is a promising candidate for solar absorber materials from the viewpoint of high absorption and earth‐abundant constitution elements. In this paper, we fabricated ZnSnP 2 crystals by flux method based on the phase diagram of Sn‐ZnP 2 pseudo‐binary system and investigated their properties for an application to photovoltaics. The crystal growth experiments with the cooling rate of 0.7 and 12 °C/h were carried out and we successfully obtained ZnSnP 2 crystals with the diameter of 8mm and the thickness of a few mm by a slow cooling rate. The structure of grown crystals studied by X‐ray diffraction was indicated to be chalcopyrite‐type ZnSnP 2 . In addition, the decrease of the degree of order was observed with the increase of cooling rate. The lattice constants of a and c axes are 5.649 and 11.295 Å, respectively. The composition of grown crystals is a near stoichiometric ratio of ZnSnP 2 by EDX analysis. The bandgaps of ZnSnP 2 crystals obtained by cooling rate of 0.7 and 12 °C/h were estimated to be 1.61 and 1.48 eV, respectively, which is caused by the difference of the degree of order. The hall‐resistivity measurement showed that ZnSnP 2 crystals with a slow cooling rate has a p‐type conduction. The resistivity, the hole concentration and the mobility are 10∼70 Ωcm, 6·10 16 ∼2·10 17 cm ‐3 , and 1∼3 cm 2 V ‐1 s ‐1 . The obtained properties are suitable for an absorber of photovoltaics. (© 2015 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)