Near-Infrared Limitations To Silicon Photodetector Self-Calibration

Recent improvements in silicon photodiode fabrication technology and our understanding of their properties have led to NBS development of a self-calibration technique yielding errors less than 0.1% in spectral responsivity over the spectral range 400-800nm. The wavelength range beyond 800nm has not been fully explored, most likely because of the lack of convenient laser sources in this region. We have successfully used conventional sources to study the response of silicon photodiodes in this region. Several types of photodiode (conventional, inversion layer and YAG) have been characterized to determine the longest wavelength feasible for self-calibration. Comparisons of empirical results were made with device theory. The limiting factors for metallurgical-junction diodes are the ability to deplete the bulk region with sufficient reverse bias prior to the onset of breakdown and absorption at the rear surface. The maximum wavelength appears to be about 920nm.