Photon Counting UV-APD Electric Field Shaping
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Avalanche photodiodes (APDs) face challenges in optimizing their performance parameters such as gain, quantum efficiency, and cross-talk in arrayed devices, particularly in imaging applications, where individual APD detection is crucial to prevent self-sustaining impact ionization processes and minimize trigger probabilities for holes.
Innovation Solution
The design involves a silicon APD structure with a p-type absorption region and a n-type multiplication region, where epitaxial layers are in-situ doped to form a p-n junction, and implanted regions are used to shape the electric field, allowing for controlled reverse bias to enhance electron triggering while minimizing hole triggering, and featuring a backside contact for quenching mechanisms to manage self-sustaining processes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the reverse bias is increased to enhance electron triggering probability, then the gain and electron detection efficiency improve, but the hole triggering probability increases causing self-sustaining impact ionization
Solution Approach 1:
The patent applies different doping types and concentrations in different regions: the absorption region uses one doping type while the multiplication region uses another, creating locally optimized electric field distributions that favor electron triggering while suppressing hole triggering at the same reverse bias level
Solution Approach 2:
The patent optimizes the doping concentration parameters in the absorption and multiplication regions to create an asymmetric electric field profile that enhances electron impact ionization probability while reducing hole impact ionization probability, allowing higher reverse bias operation without self-sustaining discharge
2Reliability
If the multiplication region is expanded to increase gain, then more electron-hole pairs are generated, but cross-talk between adjacent APDs in arrays increases
Solution Approach 1:
The patent divides the semiconductor structure into distinct absorption region and multiplication region with clearly defined boundaries, confining the impact ionization process to a localized multiplication region that limits lateral charge carrier diffusion and reduces optical cross-talk between adjacent APDs in arrays while maintaining high gain
Solution Approach 2:
The patent separates the photon absorption function (in the absorption region) from the charge multiplication function (in the multiplication region), allowing the multiplication region to be optimized for gain while the absorption region can be optimized for photon detection, with the spatial separation reducing cross-talk effects
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach enhances the APD's ability to detect photons with specific wavelengths, reduces cross-talk in arrays, and improves the overall performance by concentrating the multiplication region and shaping the electric field to increase the probability of electron-induced triggering while maintaining low hole triggering, thus optimizing the APD's operational efficiency.
Implementation Method 1
Photons that are absorbed in the absorption region generate an electron-hole pair
Implementation Method 2
The strong electric field in the multiplication region accelerates the electron to a point where the electron has enough energy to generate more electron-hole pairs through impact ionization within the multiplication region
Implementation Method 3
The electron (if absorption region is p-type) drifts or is carried by a low-level electric field to the multiplication region
Data Source
AI summary
An avalanche photodiode (APD) has a first semiconductor substrate having a first doping type. A first semiconductor layer is on top of the first semiconductor substrate. The first semiconductor layer is doped with the first doping type. A second epitaxial layer is on top of the first semiconductor layer. The second epitaxial layer is in-situ doped with the first doping type at a concentration higher than a concentration of the first doping type in the first semiconductor layer. A third epitaxial layer is on top of the second epitaxial layer. The third epitaxial layer is in-situ doped with a second doping type. The doping of the third epitaxial region forms a first p-n junction with the doping of the second epitaxial layer, wherein a carrier multiplication region includes the first p-n junction, and wherein the third epitaxial layer forms an absorption region for photons. A first implanted region is within the third epitaxial layer. The implanted region is doped with the second doping type.