Lateral-Effect Position-Sensing Detector for SWIR Tracking
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Solution Overview
Problem
Current lateral-effect position-sensing detectors (LEPSDs) for short-wave infrared (SWIR) and mid-wave infrared (MWIR) wavelengths face challenges with high capacitance, high inter-electrode resistance, and limited bandwidth due to their design, which hinders the detection of transient events and tracking of rapidly moving objects.
Innovation Solution
A dual-axis LEPSD structure with a narrow band gap absorber, a Type III hetero-junction between the electron barrier layer and the lateral-current conducting layers, and an electron barrier designed to be >2 μm thick and depleted over most of its width, reducing dark current, inter-electrode resistance, and capacitance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the absorber layer is made thin to maximize SWIR light absorption, then light absorption efficiency is improved, but capacitance increases due to the thin I-layer between P and N layers
Solution Approach 1:
The patent introduces an intrinsic (undoped or lightly doped) absorber layer as an intermediary between the P-type and N-type lateral-current conducting layers. This intrinsic layer acts as a mediator that reduces capacitance while still allowing efficient light absorption, resolving the contradiction between thin layer design for absorption and capacitance reduction.
2Device complexity
If the depleted barrier layer thickness is reduced to achieve desired capacitance, then capacitance per unit area increases, but response bandwidth and rise time are degraded
Solution Approach 1:
The patent changes the doping parameter of the absorber layer from doped to intrinsic (undoped or lightly doped), which fundamentally alters the capacitance characteristics. This parameter change allows the device to achieve low capacitance without requiring a thin depleted barrier layer, thereby maintaining fast response bandwidth and rise time.
3Reliability
If a p-type material layer is used for lateral current conduction, then electron barrier function is achieved, but inter-electrode resistance becomes quite high
Solution Approach 1:
The patent employs a composite structure where the absorber layer is made of intrinsic semiconductor material rather than p-type material. This composite approach combines the electron barrier function with low inter-electrode resistance, as the intrinsic material does not suffer from the high resistance characteristics of p-type hole-conducting layers.
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 enhances the temporal response and bandwidth frequency response, allowing for the detection of short transient events and tracking of rapidly moving objects with a larger instantaneous field of view, while minimizing dark current and capacitance.
Implementation Method 1
the absorber layer 102 absorbs the incident light and generates electrons and holes
Implementation Method 2
the electron barrier layer 103 prevents flows of electrons from the absorber layer 102 into the electron barrier layer 103 but permits flows of holes from the absorber layer 102 into the electron barrier layer 103
Implementation Method 3
a Type III hetero-junction between the electron barrier layer and the lateral-current conducting layers
Data Source
AI summary
A lateral-effect position-sensing detector includes a second lateral-current collector layer, an electron barrier layer on the second lateral-current collector layer, an absorber layer on the electron barrier layer, a first lateral-current collector layer on the absorber layer, and a first elongate electrical contact and a second elongate electrical contact on each of the lateral-current collector layers. Incident light radiates a transparent first lateral-current collector layer to be absorbed by the undepleted absorber layer where electron and holes are generated. The depleted electron barrier layer prevents a flow of electrons from the absorber layer to the second lateral-current collector layer but allows electrons to flow to the second lateral-current collector layer. The lateral-effect position-sensing detector is sensitive to a lateral position between the first elongate electrical contact and the second elongate electrical contact of incident light on each of the lateral-current collector layer.