Lateral Single-Photon Avalanche Diode With Sidewall Doping Control
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Solution Overview
Problem
Existing avalanche diodes for Geiger-mode operation have high breakdown voltages, which can lead to inefficient detection of weak radiation due to high electric field strengths and self-sustaining avalanche currents.
Innovation Solution
A lateral single-photon avalanche diode with a semiconductor body, a trench having a sidewall with increased electric conductivity, and anode and cathode terminals arranged at the surface, where the junction region is formed by doping and a counterdoped region is introduced between the junction and the surface to reduce breakdown voltage and enhance radiation detection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the breakdown voltage is increased to enhance radiation detection, then the detection efficiency improves, but the electric field strength becomes excessively high causing self-sustaining avalanche currents
Solution Approach 1:
The patent applies local quality by creating a non-uniform doping profile where the doping concentration varies with depth. Specifically, the first doping concentration at the surface is higher than the second doping concentration at greater depths, which localizes the electric field distribution and prevents excessive field strength while maintaining effective radiation detection.
Solution Approach 2:
The patent changes the doping concentration parameter as a function of depth. By having the doping concentration decrease with increasing depth (first concentration > second concentration), the electric field distribution is optimized to achieve breakdown at appropriate voltages without creating regions of excessively high field strength that would cause self-sustaining avalanches.
2Stress or pressure
If the doping concentration is increased to reduce breakdown voltage, then the breakdown voltage becomes adjustable, but the electric conductivity increases causing higher dark current
Solution Approach 1:
The patent applies local quality by having different doping concentrations at different depths. The higher surface doping concentration facilitates breakdown at lower voltages, while the lower deeper doping concentration reduces the overall dark current, achieving both goals simultaneously through spatially varying properties.
Solution Approach 2:
The patent transitions from a uniform doping approach to a depth-dependent doping profile. By introducing the depth dimension as a variable for doping concentration, the patent can independently optimize surface properties for breakdown voltage and bulk properties for dark current suppression.
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
The solution allows for increased absorption of infrared wavelengths without raising the breakdown voltage, ensuring proper Geiger-mode operation with a constant electric field, independent of the electron-hole pair generation depth, and allows for adjustable breakdown voltage through doping concentration.
Implementation Method 1
Avalanche photodiodes having the pn junction biased in the reverse direction become conducting when the applied voltage exceeds a breakdown voltage. A single-photon avalanche diode is operated with reverse bias voltage above the breakdown voltage, in the so-called Geiger-mode.
Implementation Method 2
already few electron-hole pairs generated by incident photons and injected into the depletion layer can trigger a self-sustaining avalanche current
Data Source
Figure 1~2
Figure 3~4
Figure 5
AI summary
The lateral single-photon avalanche diode comprises a semiconductor body (1, 2) comprising a semiconductor material of a first type of electric conductivity, a trench (3) in the semiconductor body, and anode and cathode terminals (5, 6). A junction region (14) of the first type of electric conductivity is located near the sidewall (38) of the trench, and the electric conductivity is higher in the junction region than at a farther distance from the sidewall. A semiconductor layer (4) of an opposite second type of electric conductivity is arranged at the sidewall of the trench adjacent to the junction region. The anode and cathode terminals are electrically connected with the semiconductor layer and with the junction region, respectively. The junction region (14) may be formed by a sidewall implantation.