X-ray detector passivation layer reduces leakage current
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Solution Overview
Problem
Contemporary X-ray detectors face reduced detective quantum efficiency (DQE) due to electron trap phenomena at the boundary region of PIN diodes, leading to deteriorated photodetection efficiency.
Innovation Solution
The X-ray detector design includes a passivation layer and a second lower electrode formed on the upper portion of the passivation layer, which reduces leakage current in the PIN diode and maximizes the area for the PIN diode, along with a non-overlapping configuration of the gate and second lower electrodes to enhance fill factor and photodetection efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional PIN diode structure is used in the X-ray detector, then the device can be manufactured with standard processes, but electron trap phenomena occur at the boundary region leading to reduced photodetection efficiency and lower DQE
Solution Approach 1:
A passivation layer is introduced as an intermediary between the PIN diode and the gate insulating layer. This passivation layer specifically addresses the electron trap phenomena at the boundary region by providing a protective interface that eliminates harmful electron trapping, thereby improving photodetection efficiency without disrupting the standard manufacturing process
Solution Approach 2:
The detector structure is segmented into distinct functional layers with clear boundaries: the PIN diode region, the passivation layer region, and the gate insulating layer region. This segmentation allows each layer to perform its specific function optimally, with the passivation layer specifically targeting the boundary region problems while the other layers maintain their respective functions
2Reliability
If the gate electrode and lower electrode are configured to overlap, then the device structure is simplified, but the fill factor is reduced and photodetection efficiency deteriorates
Solution Approach 1:
The electrode configuration transitions from a planar overlapping arrangement to a vertically stacked arrangement in the third dimension. The gate electrode, gate insulating layer, and lower electrode are stacked vertically, allowing the electrodes to be positioned close together in the vertical dimension without occupying the same horizontal space, thereby maintaining high fill factor while ensuring proper electrical isolation and function
3Reliability
If the PIN diode area is maximized, then photodetection efficiency improves, but leakage current increases due to boundary effects
Solution Approach 1:
The passivation layer serves as a protective intermediary that specifically addresses the boundary region issues. By introducing this intermediate layer at the boundaries of the PIN diode, the structure can maximize the active detection area while the passivation layer simultaneously suppresses leakage current by eliminating electron trap phenomena at the edges
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 configuration effectively eliminates electron trap phenomena, increasing the photodetection efficiency of the PIN diode and enhancing the overall DQE of the X-ray detector.
Implementation Method 1
a scintillator layer for converting an externally incident X-ray into a visible ray
Data Source
AI summary
An X-ray detector constructed as an exemplary embodiment of the present invention includes a semiconductor layer, a data line including a source electrode covering a first portion of the semiconductor layer, a drain electrode disposed opposite to the source electrode, a first lower electrode formed on the upper portion of a second portion of the semiconductor layer and a gate insulating layer and elongated from the drain electrode, and a passivation layer formed on the upper portion of one part of the lower electrode including the drain electrode. Further, the second lower electrode is formed approaching the gate electrode. The X-ray detector constructed as the exemplary embodiment of the present invention includes a second lower electrode formed on the passivation layer and placed approaching a gate electrode. The area in which a diode is disposed may be maximized, and the amount of leakage current may be reduced.