Avalanche buildup time of silicon reach‐through photodiodes

摘要

The avalanche buildup time t, which is related to the multiplication factor (M) by t=τ1 M, where τ1 is the intrinsic response time, is studied for silicon reach‐through avalanche photodiodes (RAPD’s) by a shot‐noise measurement in the GHz region. The dependences of t on both the length of the avalanche region la and the wavelength exciting the avalanche process (λ) are investigated. The τ1 values obtained increase with la in the region la≳1.0 μm and also take larger values for λ∼6300 Å than for λ∼8300 Å. These values are in good agreement with a calculation using the modified Emmons equation τ1=Nkeffla/vs except for the very narrow avalanche region (la≲0.4 μm), where N is a constant dependent on la, keff is the effective ratio of hole to electron ionization rates, and vs is the carrier saturation velocity. These results are very useful to investigate the frequency response of RAPD’s. The diodes discussed are used extensively in fiber transmission systems.