2D Van Der Waals Avalanche IR Detector With Stepwise Homojunction
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Solution Overview
Problem
Existing thin-film avalanche photodetectors suffer from low carrier multiplication efficiency, high avalanche threshold energy, and high noise due to lattice mismatch, defect diffusion, and strong electron-phonon coupling, limiting sensitivity and signal-to-noise ratio.
Innovation Solution
An avalanche infrared detector with a homojunction layer made of two-dimensional van der Waals materials, featuring a thin-layer and thick-layer zone, and electrodes on each zone, which enhances coulomb interaction and reduces energy loss through a stepwise electric field.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If thin-film avalanche photodetectors use high reverse bias to achieve carrier multiplication, then photogain is improved, but avalanche threshold energy becomes excessively high (more than 22 times band gap)
Solution Approach 1:
The patent changes the fundamental material parameter from thin-film to two-dimensional van der Waals material, which fundamentally alters the energy-band structure and carrier multiplication mechanism. This material parameter change enables avalanche multiplication at threshold energies of only 1.1-1.5 times the band gap, dramatically reducing the threshold from >22 times band gap to near-theoretical minimum.
Solution Approach 2:
The patent creates a stepwise homojunction with localized high electric field regions at the interface between thin-layer and thick-layer zones. This localized field enhancement concentrates the avalanche multiplication effect in specific regions where the electric field is strongest, allowing efficient carrier multiplication without requiring uniformly high bias across the entire device.
2Volume of moving object
If thin-film materials are used to achieve compact structure, then device size is reduced, but carrier multiplication efficiency decreases due to momentum conservation restrictions
Solution Approach 1:
The patent transitions from three-dimensional thin-film structure to two-dimensional van der Waals material, fundamentally changing the dimensional parameter. This dimensional reduction eliminates the momentum conservation restrictions that plague thin-film materials, as 2D materials have different band structure characteristics that allow more efficient energy transfer from hot carriers to electron-hole pairs.
Solution Approach 2:
The patent constructs a composite structure combining two-dimensional van der Waals material with substrate and electrode materials. The van der Waals material layer (1-10 nm thick) maintains compact device size while its unique 2D crystal structure provides the necessary electronic properties for efficient carrier multiplication, resolving the contradiction between size and efficiency.
3Reliability
If doping is used in thin-film PN junction avalanche photodetectors to create junctions, then device functionality is achieved, but defect and impurity diffusion increases dark current significantly
Solution Approach 1:
The patent extracts and eliminates the doping process entirely from the device fabrication. Instead of using doped regions to create the PN junction, the invention uses a stepwise homojunction formed by varying the thickness of intrinsic two-dimensional van der Waals material. This extraction of the doping step removes the source of defects and impurities that generate dark current.
Solution Approach 2:
The patent introduces a stepwise homojunction structure as an intermediary mechanism to achieve charge separation and device functionality without direct doping. The interface between thin-layer and thick-layer zones of the van der Waals material creates the necessary electric field and potential difference, serving as a mediator that replaces the traditional doped junction while avoiding its harmful effects.
4Strength
If high working voltage is applied to overcome momentum conservation restrictions in thin-film materials, then carrier kinetic energy is sufficient for avalanche multiplication, but excess noise is significantly amplified
Solution Approach 1:
The patent changes the material parameter from thin-film to two-dimensional van der Waals material, which fundamentally alters the carrier acceleration and multiplication dynamics. The unique electronic structure of 2D materials allows efficient energy transfer at lower voltages, reducing carrier kinetic energy to near-theoretical minimum (1.1-1.5 times band gap) while maintaining effective avalanche multiplication, thereby minimizing excess noise generation.
Solution Approach 2:
The patent concentrates the avalanche multiplication effect in localized high-field regions at the stepwise homojunction interface rather than distributing it uniformly across the device. This localized multiplication reduces the total volume where noise can be generated and allows the device to achieve high gain with lower overall bias voltage, thereby reducing excess noise.
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 detector achieves high sensitivity, low avalanche threshold, high gain, and improved photoelectric conversion efficiency with reduced dark current components, enabling high-speed response under room-temperature conditions.
Implementation Method 1
a stepwise homojunction interface is adopted to enhance a coulomb interaction between carriers, inhibit the hot carrier-phonon coupling, and reduce an energy loss caused by a relaxation process
Implementation Method 2
inhibit the hot carrier-phonon coupling, and reduce an energy loss caused by a relaxation process
Implementation Method 3
Avalanche photodetectors are a class of typical devices based on hot carrier multiplication. Hot carriers undergo continuous collisional ionization under high reverse bias conditions to allow the multiplication of geometric progressions of photo-generated electrons and holes
Data Source
AI summary
The present application relates to an avalanche infrared detector and a preparation method thereof. In the present application, a homogeneous structure is constructed based on an atomic layer number-dependent energy band structure of a two-dimensional van der Waals material, which can solve problems such as lattice mismatch and defects of the traditional heterojunction avalanche photodetectors and can inhibit the generation of main dark current components such as recombination current and tunneling current by detectors. A “peak” electric field at a stepwise homojunction interface is adopted to enhance a coulomb interaction between carriers, inhibit the hot carrier-phonon coupling, and reduce an energy loss caused by a relaxation process. The avalanche infrared detector provided by the present application can exhibit advantages such as high-speed response, high sensitivity, low avalanche threshold, and high gain under room-temperature working conditions, which expands an application range of the avalanche infrared detector.