研究目的
To accurately and efficiently estimate the design space of heterostructure avalanche photodiodes (APDs) in terms of gain, noise, and bandwidth without full Monte Carlo simulations, and to compare GaAs p-i-n APDs with staircase structures.
研究成果
The improved RPL algorithm effectively models complex heterostructure APDs, showing that staircase APDs offer advantages in excess noise reduction over p-i-n diodes, but gains in gain-bandwidth product are limited unless hole impact ionization is suppressed. The method enables exploration of the design space for gain, noise, and bandwidth.
研究不足
The model underestimates the experimental breakdown voltage for staircase APDs, and the computational approach, while efficient, may sacrifice some accuracy compared to full Monte Carlo simulations. The assumption of constant carrier velocities and negligible photo-generated current effects on electrostatics could be limitations.
1：Experimental Design and Method Selection:
The improved Random Path Length (RPL) algorithm is used, extending beyond the Dead Space concept by incorporating a nonlocal model for impact ionization based on effective fields derived from energy balance equations. This allows handling of heterostructures like staircase APDs and p-i-n diodes.
2：Sample Selection and Data Sources:
GaAs and Al_xGa_{1-x}As p-i-n APDs and a specific staircase structure from literature [15] are used, with model parameters calibrated from previous work.
3：List of Experimental Equipment and Materials:
No specific equipment listed; simulations are computational.
4：Experimental Procedures and Operational Workflow:
The RPL algorithm involves generating random path lengths for carriers using equations (1)-(6), simulating carrier motion, impact ionization, and current waveforms via Ramo's theorem. Multiple stochastic runs are performed to compute average gain, noise, and bandwidth.
5：Data Analysis Methods:
Results are compared with finite difference implementations and experimental data from references; Fourier transforms of current waveforms are used to determine bandwidth.
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