A study of InGaAs/InAlAs/InP avalanche photodiode

• Characteristics of SAGCM APD were studied.
• Doping of buffer layer in APD strongly influences breakdown voltage value.
• Modifications of absorbing layer preserving APD’s breakdown voltage were found.
• SAGCM APD with Gain Bandwidth Product of at least 115 was fabricated.
• Optical immersion significantly improves APD’s photoresponse.

Development of telecommunication, medical imaging and measurement systems resulted in increasing demand for new generation of photodetectors, especially those with internal gain. An example of such device is Separate Absorption, Grading, Charge and Multiplication Avalanche Photodiode. It achieves far greater sensitivity, faster response time and smaller dark current levels in comparison with conventional p–n or p–i–n avalanche photodiodes. Additionally, to improve parameters of the photodiode an integrated monolithic optics can be applied.In this work numerical analysis of selected regions in such avalanche photodiode operating at 1.55 μm wavelength was performed. Calculations were carried out using Silvaco’s TCAD software. The influence of doping concentration, profile and layer thickness on device characteristics was investigated. The results of performed simulations were then compared with data obtained from the measurements of real avalanche photodiodes.