Si-based n++-p–-p+-p–-p++ avalanche diode: Self-consistent modeling for infrared optoelectronic applications

A theoretical approach for modeling electric and photoelectric characteristics of specifically designed Si-based n++-p–-p+-p–-p++ avalanche photodiodes has been developed. The electrostatic characteristics (band bending, built-in electrostatic fields and carrier distributions) and current-voltage characteristics including photocurrent and diode sensitivity to electromagnetic radiation of the near-infrared spectral range have been calculated and analyzed for the room operation temperature. The measured doping profiles in the fabricated prototype of the avalanche Si-based photodiode have been used in the calculations. For a particular set of the photodiode parameters, we have found that the avalanche transport regime occurs at the applied reverse voltage of ~ –47 V across the diode length of 380 μm We have established that the rapid exponential growth of the current densities from 0.01 to 100 μA/cm2 in the range of the applied voltages of –40 to –47 V is inherent for formation of the avalanche-type transport regime. At this, considerable photoresponsibility values of 100 to 30 A/W are predicted for electro-magnetic radiation wavelengths of 0.8 to 1 μA. All the results have been obtained using literature data on field dependences of the impact ionization coefficients, spectral dependences of the optical permittivity (refractive index and extinction coefficient), etc.