Noise Characteristics in Silicon Photodiodes

Measurements of noise spectral density in the avalanche multiplication region have been made from 1 MHz to 4 GHz for four silicon photodiodes. The noise spectral density has been compared with the existing theories. At low frequencies the microplasma on-off noise, the theory of which has been successfully applied to one diode containing a single bistable microplasma, is pronounced. At high frequencies (≥100 MHz) one of the photodiodes exhibited a uniform-avalanche shot noise, which has been well described by McIntyre's theory with k=0.1, where k is the ratio of the hole ionization coefficient to the electron ionization coefficient. The rf (1 MHz~1 GHz) bias has been found to give rise to shifts of the I–V curves to higher voltages and changes in the noise spectral density. In some cases the noise spectral density is reduced. However, whether the noise is reduced or not depends on the property of microplasmas contained in the diode.