Interface traps created by amorphous silicon(a-Si)deposition using dc magnetron sputtering or a microwave plasma-enhanced chemical vapor deposition method ontop-type crystalline silicon(c-Si)substrates in solar cell structures were studied by thermally stimulated capacitance. The trap properties (type, energy, and concentration) have been estimated as a function of various cell fabrication conditions. Plasma deposition ofa-Siis seen to induce electron traps when thec-Sisubstrates are pretreated with hydrofluoric acid, and hole traps when a thin oxide layer is initially present on thec-Si.A strong correlation is observed between the trap activation energies when electron trapping centers are present and the corresponding photoresponse of these solar cells. Solar cells with 10&percent; efficiency fabricated bya-Sisputtered at 64 W of power, exhibit3×1014 cm−3trapping centers with an activation energy of 0.44 eV. ©1997 American Institute of Physics.