Staircase Avalanche Photodiodes
Abstract
The internal gain of avalanche photodiodes (APDs) can provide higher sensitivity for communications and sensing applications than p-i-n photodiodes. However, the origin of the APD gain is impact ionization, a stochastic process that results in excess noise and limits the gain-bandwidth. For the past four decades, reducing the excess noise factor has been a focus of APD research and development. One approach has been to identify materials with advantageous impact ionization characteristics such as HgCdTe and Si. Another approach to achieving low noise is through incorporating new materials and impact ionization engineering with appropriately designed heterostructures. One structure that was proposed to achieve very low noise is the staircase APD. Avalanche events occur proximate to sharp bandgap discontinuities, which function similarly to dynodes in a photomultiplier tube. In a previous ARO program, we have demonstrated Ð for the first time Ð staircase gain in a single step staircase structure based on the AlxIn1-xAsySb1-y material system, which was grown by molecular beam epitaxy. Since that staircase APD utilized a single staircase step in the multiplication layer, the maximum gain was two. In this program, we propose to extend that groundbreaking work to APDs with multiple steps in order to achieve high gain while maintaining ultra-low noise. It was also found in the previous program that proper design could produce a new type of photodetector that exhibited high photoconductive gain at ~ 2V bias. In this program, we will (1) extend our previous work on the staircase APD with multiple steps in order to achieve high gain while maintaining ultra-low noise and decreasing the dark current and (2) optimize the design of the staircase structure to achieve high photoconductive gain at low bias. These photodetectors have the potential to significantly impact high-gain/high-bandwidth and low-power thermal imaging applications, respectively.
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Feb 14, 2019
- Source ID
- W911NF1710065
Entities
People
- Seth R. Bank
Organizations
- Army Contracting Command
- Defense Advanced Research Projects Agency
- University of Texas at Austin