The conduction type in (Zn,Sn,Mn)As-2 thin films grown by molecular beam epitaxy (MBE) on InP substrates was found to be controllable from p-type to n-type as a function of Mn content. n-type (Zn,Sn,Mn)As-2 thin films were obtained by Mn doping of more than approximately 11 cat.%. It is likely that Mn interstitials (Mn-I) incorporated by excess Mn doping are located at tetrahedral hollow spaces surrounded by Zn and Sn cation atoms and four As atoms, which are expected to act as donors in (Zn,Sn,Mn)As-2, resulting in n-type conduction. The effect of annealing on the structural, electrical and magnetic properties of n-type (Zn,Sn,Mn)As-2 thin films was investigated as functions of annealing temperature and time. It was revealed that even if the annealing temperature is considerably higher than the growth temperature of 320 degrees C, the magnetic properties of the thin films remain stable. This suggests that a Mn-I complex surrounded by Zn and Sn atoms is thermally stable during high-temperature annealing. The n-type (Zn,Sn,Mn)As-2 thin films may be suitable for application as n-type spin-polarized injectors. (C) 2018 Elsevier B.V. All rights reserved.