A semiconductor that can be doped to be either p-type or n-type is of great importance, as p-n homojunctions are desirable for realizing various electronic devices and processes. However, because of pervasive doping asymmetry for wide band gap semiconductors, the achievement of both p-type and n-type in a single wide gap material is very difficult. Here, we report the success in developing a new transparent magnetic NixCu1-xI halide semiconductor that can be either p-type or n-type depending on Ni fraction in NixCu1-xI. For 0 ≤ x ≤ 0.10, NixCu1-xI films show p-type conductivity. For the range 0.15 ≤ x ≤ 0.35, NixCu1-xI films show an n-type character. The NixCu1-xI films are electrically conducting and optically transparent and show soft ferromagnetic behavior with an optimum conductivity of 42 S cm-1 (x = 0.03) and visible light transmission of 80%. Ultraviolet photoelectron spectroscopy studies on NixCu1-xI films reveal the systematic Fermi level shift toward the conduction band with respect to the valence band as a function Ni concentration. X-ray photoelectron spectroscopy analysis on Ni and I peak positions reveals Ni+2 valence for Ni in NixCu1-xI films, with signatures of Ni-I bonding. The observed p-type behavior originates from Cu vacancy, while the n-type character is identified to originate from the electron donor states generated by Ni incorporation in NixCu1-xI. The constructed homojunction with p-Ni0.0Cu1.0I/n-Ni0.16Cu0.84I shows a characteristic p-n junction behavior with a good rectification ratio of 2 × 102. This new type of NixCu1-xI transparent semiconductor with a tunable carrier type and magnetism may be a candidate for halide-based optoelectronic as well as spintronics development.
Keywords: copper iodide; magnetic halide semiconductor; n-type Ni incorporated copper iodide; p−n homojunction; transparent conductor.