K. Ramachandran, A. Muthukumarasamy, S. Chidambaram, and R. Gunarasan, “Review on conductivity enhancement in n-ZnO/p-Si heterojunction diodes with the influence of Rare earth ions as donor impurities”., JAC, vol. 12, no. 27, pp. 5851–5858, Jan. 2017.