Avalanche photodiodes (APD) can amplify the photoelectric signal based on the avalanche multiplication effect of carrier to improve the sensitivity of detection. They have the characteristics of low noise and high gain, so they are suitable for long-distance optical communication. In this work, a multi-stage avalanche photodiode structure with SAGCM (Separated Absorption, Grading, Charge and Multiplication region) is proposed based on Impact Ionization Engineering (I2E). The photocurrent, dark current, electric field, gain and noise characteristics of InGaAs/InAlAs avalanche photodiodes are studied by optimizing the grading layer's thickness and doping concentration. According to the final simulation results, the optimized avalanche photodiodes has low excess noise. At 60 V voltage and 300 K temperature, the noise factor k value (the ratio of impact ionization coefficients) of the five-stage APD is 0.012, and the gain can reach 430.
InAs/GaSb Type II Superlattice (T2SL) has become a highly competitive material for Infrared (IR) detector. We designed a pπMn mid-wavelength infrared detector based on the InAs/GaSb T2SL materials and studied the influence of the detector structural parameters on the dark current density magnitude and the Quantum Efficiency (QE) from the theoretical simulation level. Through the simulation of the detector material and structure, the dark current density characteristics at various doping concentrations, the dark current density characteristics and QE at different superlattice material thicknesses, and the temperature dependence of the dark current level are calculated. The M-structure barrier is inserted in between the π and n layers of the T2SL infrared detector structure, and the overall dark current level can be effectively reduced. Under the condition of 77 K, according to the final simulation data results, the dark current density can achieve 9.46×10-8 A/cm2, and the peak QE can achieve 34.3%.
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