Multi-step Multiplication Structure with Low Excess Noise for the AlInAsSb Avalanche Photodiode

We report on a multi-step multiplication structure to improve avalanche photodiode (APD) device performance using impact ionization engineering, which optimizes multiplication regions. The photocurrent, dark current, gain, and noise characteristics are studied. By optimizing the step structure of the multiplication region, the impact ionization coefficient ratio k of the AlInAsSb APD for traditional, single-step, double-step, and triple-step multiplication is 0.035, 0.028, 0.0254, and 0.0238, respectively, forming a declining trend. With an increasing gain of 14.4%, the gain can reach 381. And the results are generally consistent with the experimental results in previous research. Moreover, with the same multiplication region, by changing the Al component, the bandgap difference of the multiplication layer can reduce the excess noise of the device. By changing the bandgap difference, the k value of the multiplication region with a triple step decreases from 0.0238 to 0.0231. The final optimized results show that the multi-step APD has extremely low excess noise. The k value of the triple-step structure is 0.0231. This newly designed APD with a multi-step multiplication structure can provide a good foundation for subsequent specific experiments.