Gallium nitride (GaN) and related materials have attracted an intense interest in their potential applications in high-power switching, high-temperature, and high-frequency device applications. A major advantage of the GaN system for optical applications is that the energy band gap can be reduced by alloying with InN. The InGaN alloy can provide a coverage from the near UV to the near infrared, including the visible spectrum. This research will provide the photonic and electrical properties of InGaN photo-devices by simulation. GaN and InGaN photo-devices, such as p-i-n and n-i-n devices, were simulated using ATHENA and ATLAS developed by Silvaco International, Inc. The spectral responsivity and the dark current were evaluated. These simulation results are comparable to the experimental result by Kung et al. with a 400 x 400 mum mesa structure of p-i-n GaN (SPIE 3287 (1998) 214). Since the heavily p-doping is still relatively hard to achieve currently, n-i-n photo-devices are evaluated and compared to p-i-n devices. (C) 2003 Elsevier B.V. All rights reserved.