Study Of Diffusion Length In Two-Dimensional Hgcdte Avalanche Photodiodes By Optical Beam Induced Current

Optical beam induced current (OBIC) imaging has been used to measure the diffusion length of HgCdTe avalanche photodiodes (APDs) having a cylindrical structure. We show that the effective diffusion length extracted from current profiles is dependent on the electrode size and shape and the distance between electrode and excitation spot. To obtain the bulk diffusion length, a two-dimensional diffusion model was developed. The simulations provide good fits to experiment and indicate a bulk diffusion length of 70 mu m at room temperature. (c) 2005 American Institute of Physics.