p-type cupric oxide (p-CuO) thin films on n-type silicon substrates were grown to make p-CuO/n-Si heterojunctions. The CuO deposition on Si was carried out using radio frequency (RF) magnetron sputtering followed by rapid thermal annealing at 350°C. Plasma nitridation was used to incorporate nitrogen (N) for improving the electrical conductivity of the CuO thin films. The crystalline structure and surface composition of RF-sputtered CuO were characterized by x-ray diffraction and x-ray photoelectron spectroscopy. It was observed that the introduction of nitrogen in CuO improves the photovoltaic properties, such as the open-circuit voltage, short circuit current, and the photocurrent of the p-CuO-n-Si heterojunction.