Order Disorder Phenomena and Their Effects on Bandgap in ZnSnP2

A ternary compound semiconductor ZnSnP2 has the order disorder transition, where the ordered and disordered phases are chalcopyrite (I (42) over bard, a = 5.651 angstrom, c = 2a) and sphalerite (F (43) over barm, a = 5.651 angstrom), respectively.In this study, the quantitative relationship between bandgap and long-range order parameter was investigated by analyzing ZnSnP2 bulk crystals obtained by various cooling rates in crystal growth. The Chipman and Warren method was used to evaluate the long-range order parameters from X-ray diffiaction profiles. The results showed that the long-range order parameter ri decreases from 0.94 to 0.54 with the increase in cooling rates, and the bandgap gradually reduced from 1.60 to 1.37 eV, corresponding to the eta value. It was also demonstrated that bandgap tuning of ZnSnP2 was possible by controlling the long-range order parameter through annealing process. This study clarified the effects of the order disorder phenomena on bandgap in a model material, ZnSnP2, based on the evaluation of long-range order parameter, which is also a promising technique to tune the bandgap without composition control.