Fabrication and characterization of nitrogenated tetrahedral amorphous carbon (ta-C:N) semiconductor/crystalline p-type silicon (p-Si) heterojunction structures are reported. The electron-hole pairs generated from both ta-C:N and Si depletion regions were observed from photoresponse measurements. The peaks are centered at about 540 and 1020 nm, which correspond to the optical absorption edge of ta-C:N and p-Si, respectively. The reverse current increased by three orders of magnitude when the structures were exposed to AM1 light. A photovoltaic effect was observed from ta-C:N and the values of short circuit current, open circuit voltage, and field factor obtained are 5.05 mA cm−2, 270 mV, and 0.2631, respectively. © 1998 American Institute of Physics.