Theoretical Study and Monte Carlo Simulation of III-V Compound Photodiodes

A Monte Carlo simulation tool is developed to theoretically study the
characterisics of avalanche photodiodes (APDs) and high-power photodiodes and to design new structures with enhanced performance. Consistency is achieved between experiments and simulations.
With respect to APDs, I have studied the noise of an InAlAs/InAlGaAs
tandem APD structure. My simulations reproduced previous experimental results. I then used the model to modify the structure in order to achieve lower excess noise. The new device has been fabricated and confirms my prediction of lower noise.
Recently it has been reported that InAs APDs can achieve extremely low noise. In this dissertation, two InAs APD structures are designed and fabricated. They exhibit low dark current and low excess noise factors. An AlAsSb blocking layer is used in orderto further improve performance. Lower dark current and significantly higher gain have been demonstrated. Monte Carlo simulation is also used to investigate the bandwidth enhancement effect in APDs at high photocurrent levels. The non-linear behavior of these photodiodes is studied by considering the APD as a mixer and characterizing the conversion efficiencies.
Photonic microwave signal generation has been used to generate microwave
signals with extremely low phase noise. It has been observed in experiments that the total shot noise contributes unequally to phase noise and amplitude noise. An analytical model developed at NIST explains the imbalance effect but cannot replicate the observed saturation behavior of the phase noise level. Through Monte Carlo simulation I have shown that the randomness in carrier transport contributes to excess shot noise, which significantly affects the phase noise level and explains the saturation phenomenon.