Optimization of charge and multiplication layers of 20‐Gbps InGaAs/InAlAs avalanche photodiode

We calculated the correlation between the doping concentration of the charge layer and the multiplication layer for separate absorption, grading, charge, and multiplication InGaAs/InAlAs avalanche photodiodes (APDs). For this purpose, a predictable program was developed according to the concentration and thickness of the charge layer and the multiplication layer. We also optimized the design, fabrication, and characteristics of an APD for 20 Gbps application. The punch‐through voltage and breakdown voltage of the fabricated device were 10 V and 33 V, respectively, and it was confirmed that these almost matched the designed values. The 3‐dB bandwidth of the APD was 10.4 GHz, and the bit rate was approximately 20.8 Gbps.