Avalanche Photodiodes for Enhanced Photon Counting Performance at 1.5 um

APDs offer tremendous potential for the numerous applications in which photon densities are extremely low and the ability to count single photons is essential. Researchers have recently found that the optimization of InP-based APDs for counting photons may require innovative design approaches that are quite distinct from those shown to optimize APD linear mode performance. For this program, we propose to design and fabricate InP-based APDs for which the avalanche dynamics are optimized specifically for photon counting using design concepts that incorporate novel bandgap engineering approaches. In particular, these concepts will allow us to achieve increased detection efficiency at 1.5 um with simultaneous reduction of the dark count rate through the use of impact ionization engineering multiplication regions. COMMERCIAL APPLICATIONS: There are numerous optically power-starved applications for which the ability to effectively count photons at 1.5 um is critical, including: quantum cryptography and quantum key distributions, lidar systems and active remote sensing optical instruments; eye-safe military lidar applications, including range-finding and three-dimensional imaging; optical time domain reflectometry; detection of photoemission process, as in semiconductor diagnostics; and free-space optical communications. In some cases, the development of higher performance photon counting detectors will vastly improve overall system performance, In other cases, the advent fo better detectors will make these systems far more cost effective, e.g., by relaxing the present requirements on transmitter performance.