III-V Pixel X-Ray Detector Passivation for Leakage Suppression
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Solution Overview
Problem
Existing III-V semiconductor pixel X-ray detectors suffer from residual or leakage currents, particularly at the edges of planar pn junctions or mesa structures during reverse bias operation.
Innovation Solution
A III-V semiconductor pixel X-ray detector design with a semiconductor passivation layer of a different energy band gap, spaced at a minimum distance from semiconductor contact regions, and optionally a semiconductor contact layer, to suppress leakage currents, featuring a matrix arrangement of semiconductor contact regions and metallic connections.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If planar pn junctions or mesa structures are used in III-V semiconductor pixel X-ray detectors, then X-ray detection capability is achieved, but residual or leakage currents occur during reverse bias operation particularly across the edges
Solution Approach 1:
The detector structure is segmented into distinct functional regions: an absorption region for X-ray detection and separate contact regions for electrical connection. This segmentation isolates the high-field junction edges from the contact areas, reducing leakage currents at critical interfaces while maintaining detection functionality.
Solution Approach 2:
An intermediate layer is introduced between the absorption region and the contact regions. This intermediary structure modifies the electric field distribution and provides a transition zone that suppresses leakage currents at the junction edges without directly interfering with the X-ray detection process in the absorption region.
2Measurement precision
If reverse bias voltage is increased to improve X-ray detection sensitivity, then detection sensitivity increases, but leakage currents increase particularly at junction edges
Solution Approach 1:
The electrical parameters of the detector are optimized by controlling the doping concentrations and thicknesses of different regions. The absorption region is designed with specific dopant levels to achieve high breakdown voltage and low leakage current, allowing operation at high reverse bias voltages for improved sensitivity without excessive leakage.
Solution Approach 2:
The intermediate layer acts as a mediator that manages the electric field distribution under high reverse bias conditions. It prevents field concentration at junction edges that would otherwise lead to increased leakage currents, enabling the detector to operate at high voltages for enhanced sensitivity.
3Area of stationary object
If contact regions are placed close to absorption region edges to reduce device area, then device area is reduced, but leakage currents increase at the edges
Solution Approach 1:
The detector is divided into spatially separated functional zones: the absorption region for X-ray interaction and the contact regions for electrical connection. This segmentation allows the contact regions to be positioned away from the absorption region edges, reducing leakage currents while maintaining compact overall device area through optimized layout.
Solution Approach 2:
The contact regions are arranged in a matrix pattern on the detector surface, utilizing two-dimensional spatial arrangement to optimize both area utilization and leakage current suppression. This dimensional arrangement allows sufficient spacing from absorption region edges while maintaining high pixel density.
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 design achieves low reverse currents of less than 1 µA at high reverse voltages, enabling high sensitivity and efficient X-ray detection with high breakdown field strengths, reducing patient exposure and image acquisition time.
Implementation Method 1
a semiconductor passivation layer of the first or second conductivity type lattice-matched to the absorption region and with an energy band gap different from the first energy band gap of the semiconductor contact regions
Implementation Method 2
an absorption region of a first conductivity type having a top side and a bottom side
Data Source
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Figure 6~7
AI summary
III-V semiconductor pixel X-ray detector, comprising an absorption region of a first or second conductivity type, at least nine semiconductor contact regions of the second conductivity type arranged in a matrix along the top of the absorption region, and optionally a semiconductor contact layer of the first conductivity type, wherein a metallic front-side terminal contact is arranged below the absorption region and a metallic back-side terminal contact is arranged above each semiconductor contact region, and the X-ray detector comprises a semiconductor passivation layer of the first or second conductivity type, wherein the semiconductor passivation layer and the absorption region are lattice-matched to each other.the semiconductor passivation layer is arranged regionally on the top side of the absorption region and the semiconductor passivation layer has a minimum distance of at least 2 pm or at least 20 µm to each highly doped semiconductor contact region along the top side of the absorption region.