Single-Photon Detector Layer Structure for Edge Breakdown Control
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Solution Overview
Problem
Conventional methods for making single-photon detectors, such as SPADs, face challenges including premature edge breakdown, complex fabrication processes, and low yield, especially when forming large detector arrays.
Innovation Solution
A method involving the growth of an epitaxial multi-layer structure with a buffer layer, absorption layer, transition layer, field control charge layer, multiplication layer, inversion layer, migration layer, and Ohmic contact layer, followed by a single diffusion process to form a curved diffusion region and mesa structure, and the formation of p-type and n-type electrodes, which simplifies the fabrication and reduces premature edge breakdown.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional methods (two diffusion processes) are used to make SPAD detectors, then premature edge breakdown is mitigated, but manufacturing complexity increases and yield decreases
Solution Approach 1:
The patent combines multiple diffusion processes into a single diffusion process by designing a specific epitaxial structure with multiple layers (buffer layer, absorption layer, transition layer, field control charge layer, multiplication layer, intrinsic layer) that are sequentially formed. This merging reduces fabrication complexity while maintaining the ability to mitigate premature edge breakdown through the field control charge layer and optimized layer structure.
Solution Approach 2:
The patent segments the detector structure into distinct functional layers with specific doping concentrations and thicknesses. The field control charge layer is segmented from other layers and positioned specifically to control the electric field distribution, allowing premature edge breakdown mitigation without requiring multiple diffusion processes. Each layer is optimized independently for its specific function.
2Reliability
If conventional methods (two diffusion processes) are used to make SPAD detectors, then premature edge breakdown is mitigated, but manufacturing yield decreases
Solution Approach 1:
The patent merges multiple diffusion steps into a single diffusion process by designing an epitaxial structure where the field control charge layer and other layers are sequentially formed in one continuous process. This reduces the number of process steps, increases manufacturing yield, and maintains reliability through the optimized layer structure that controls electric field distribution.
Solution Approach 2:
The patent performs preliminary actions by pre-designing the epitaxial layer structure with specific doping concentrations and thicknesses before the single diffusion process. The field control charge layer is pre-positioned and pre-doped to the appropriate concentration, so that a single subsequent diffusion process can complete the structure formation without requiring multiple diffusion steps, thereby increasing yield.
3Power
If SPAD operates above breakdown threshold voltage (Geiger mode), then high gain is achieved, but premature edge breakdown occurs
Solution Approach 1:
The patent applies local quality by creating a field control charge layer with specific doping concentration (1×10^16 to 1×10^18 atoms/cm³) and thickness (100 nm to 1 µm) at a specific position within the detector structure. This localized doping creates a controlled electric field distribution that prevents premature edge breakdown at high operating voltages while maintaining high gain in Geiger mode. The transition layer and multiplication layer are also optimized locally for their specific functions.
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 reduces the complexity of fabricating single-photon detectors, increases yield, and is suitable for forming detector arrays with improved reliability and efficiency, mitigating premature edge breakdown and dark count issues.
Implementation Method 1
Light is composed of photons which are the smallest unit of electromagnetic radiation. A single photon in the visible or near infra red range of the electromagnetic spectrum has approximately 10-19 joules of energy, and cannot be effectively detected with conventional photodetectors.
Implementation Method 2
SPADs operates via impact ionization which causes an avalanche current to develop. In terms of practicality, SPADs functions in the visible and near infra red range of the electromagnetic spectrum, has advantages such as high gain, low noise to gain ratio, low power consumption, and small size
Data Source
AI summary
A method of making a single-photon detector includes growing an epitaxial multi-layer structure that includes a buffer layer, an absorption layer, a transition layer, a field control charge layer, a multiplication layer, an inversion layer, a migration layer, a window layer, and an Ohmic contact layer sequentially on a substrate. A curved diffusion region is formed in the window layer and the Ohmic contact layer via a diffusion process. A mesa structure is formed by etching the epitaxial multi-layer. A light input window is formed on the substrate. A p-type electrode is formed on the Ohmic contact layer, and an n-type electrode is formed on the substrate. The inversion layer provides supplementary regulation of an electric field distribution that is regulated by the field control charge layer. A single-photon detector made from the method, and a single-photon detector array made with a multitude of the single-photon detectors are also provided.