We report on the optimum geometric design of In0.53Ga0.47As metal-semiconductor-metal ( MSM ) photodetectors for maximizing external quantum efficiency with transparent indium tin oxide (ITO)-based interdigitated fingers. Both ITO finger and conventional metal finger MSM photodetectors were fabricated to verify the simulated external quantum efficiency and good agreement between experimental and simulated results was obtained. In all cases, the ITO provided higher efficiencies, particularly at short finger gap spacings. (c) 2007 The Electrochemical Society.