GaN/InGaN Scintillator Stack for High-Intensity Low-Afterglow Detection
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Solution Overview
Problem
Scintillators with quantum well structures experience distortion due to differing lattice constants, leading to decreased luminescence intensity and increased afterglow, which hinders high-speed detection in charged particle beam apparatus.
Innovation Solution
A scintillator configuration with a substrate, buffer layer, stacked luminescent and barrier layers, and a conductive layer, where the barrier layer is thicker than the luminescent layer, with a thickness ratio of 11 to 25, and Si-doped to improve carrier mobility, reducing afterglow intensity while maintaining luminescence intensity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If layers containing GaN, InGaN, and the like are alternately stacked to form a quantum well structure, then luminescence intensity increases, but distortion occurs in the structure and afterglow intensity increases
Solution Approach 1:
The patent applies parameter changes by precisely controlling the thickness of the barrier layer and luminescent layer, and adjusting the composition ratio of InGaN. By setting the barrier layer thickness to 3-10 nm and InGaN composition to 0.2-0.4, the patent optimizes the quantum well structure to achieve high luminescence intensity while suppressing afterglow, resolving the contradiction between improving luminescence and reducing afterglow.
Solution Approach 2:
The patent applies local quality by creating a quantum well structure with alternating layers of different materials (GaN barrier layers and InGaN luminescent layers) with specific thickness ratios. This localized structural design with precise thickness control (b/a ratio of 0.3-1.0) enables different regions to have different functions: the barrier layers suppress carrier overflow to reduce afterglow, while the luminescent layers provide high luminescence intensity.
2Object-generated harmful factors
If the barrier layer thickness is increased to reduce afterglow, then afterglow intensity decreases, but luminescence intensity may decrease
Solution Approach 1:
The patent resolves this contradiction by optimizing the barrier layer thickness to a specific range of 3-10 nm. This parameter optimization ensures that the barrier is thick enough to suppress carrier overflow and reduce afterglow, but not so thick that it prevents carrier injection into the luminescent layer, thereby maintaining high luminescence intensity while reducing afterglow.
Solution Approach 2:
The patent uses composite materials by creating a quantum well structure with alternating layers of GaN barrier layers and InGaN luminescent layers. This composite structure leverages the different properties of each material: GaN provides high barrier height to suppress carrier overflow (reducing afterglow), while InGaN provides high luminescence efficiency. The optimized thickness ratio ensures both functions work effectively together.
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 achieves increased luminescence intensity and decreased afterglow intensity, allowing for high-speed and accurate detection in charged particle beam apparatus.
Implementation Method 1
Light generated by the scintillator due to collision of electrons
Implementation Method 2
converted into an electric signal by a photodetector such as a photoelectric tube
Data Source
AI summary
The purpose of the present invention is to provide a scintillator for a charged particle beam device and a charged particle beam device which achieve both an increase in emission intensity and a reduction in afterglow intensity. This scintillator for a charged particle beam device is characterized by comprising a substrate (13), a buffer layer (14) formed on a surface of the substrate (13), a stack (12) of a light emitting layer (15) and a barrier layer (16) formed on a surface of the buffer layer (14), and a conductive layer (17) formed on a surface of the stack (12) and by being configured such that the light emitting layer (15) contains InGaN, the barrier layer (16) contains GaN, and the ratio b/a of the thickness b of the barrier layer (16) to the thickness a of the light emitting layer (15) is 11 to 25.