IDCA Photodetector Barrier Layer Dark Current Reduction
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Solution Overview
Problem
Existing thermal imaging devices using mid-wavelength infra-red detectors require cryogenic cooling, are costly, and suffer from high dark noise due to depletion region effects, surface states, and thermal generation currents, limiting their performance and operational temperature.
Innovation Solution
A photo-detector design featuring a photo-absorbing layer with a barrier layer that prevents majority carrier tunneling and thermalized carrier flow, allowing for operation without a depletion layer and reducing dark current, which is sensitive to the 3-5 μm wavelength range and functional at higher temperatures without the need for passivation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If cryogenic cooling is used to reduce dark current, then dark current is reduced, but device cost and complexity increase
Solution Approach 1:
The patent extracts and eliminates the depletion region from the detector structure by using a Schottky contact configuration. This removes the source of SRH generation current, allowing the detector to operate without cryogenic cooling while maintaining low dark current levels.
Solution Approach 2:
The patent changes the operational parameters by operating the detector at room temperature rather than cryogenic temperatures. This is achieved through the barrier layer design that prevents thermalized majority carriers from reaching the contact, eliminating the need for temperature-based dark current suppression.
2Object-generated harmful factors
If passivation is applied to reduce surface current, then surface current is reduced, but manufacturing cost and complexity increase
Solution Approach 1:
The patent extracts and removes the need for passivation by using a Schottky contact configuration where the barrier layer itself provides the necessary isolation. The metal-semiconductor interface creates a natural barrier that eliminates surface state effects without requiring additional passivation layers or processes.
3Reliability
If depletion region is used for carrier separation, then carrier separation is achieved, but dark current increases due to SRH generation
Solution Approach 1:
The patent introduces a barrier layer as an intermediary between the semiconductor and the contact. This barrier layer mediates carrier transport by allowing photogenerated carriers to pass while blocking thermalized majority carriers, achieving carrier separation without creating a depletion region that would generate SRH current.
Solution Approach 2:
The patent replaces the depletion region mechanism with a Schottky barrier mechanism. Instead of using a p-n junction depletion region for carrier separation, the patent uses the electric field at the metal-semiconductor interface to achieve the same function without the harmful SRH generation effects.
4Ease of operation
If operating temperature is increased, then device operation is simplified, but dark current increases
Solution Approach 1:
The patent extracts and eliminates the thermal generation current by removing the depletion region where thermal generation occurs. The Schottky contact configuration with its barrier layer prevents thermalized majority carriers from being generated and transported to the contact, enabling room temperature operation.
Solution Approach 2:
The patent changes the operational temperature parameter from cryogenic to room temperature by fundamentally changing the detector structure. The barrier layer design allows the detector to maintain low dark current at higher temperatures where thermal generation would normally be problematic.
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 significantly reduces dark current noise, enables operation at higher temperatures, and eliminates the need for costly passivation, resulting in improved thermal imaging device performance, longer operation, reduced power consumption, and lighter designs.
Implementation Method 1
The barrier layer exhibits a thickness sufficient to prevent tunneling of majority carriers from the photo-absorbing layer to the contact layer
Implementation Method 2
a band gap barrier sufficient to block the flow of thermalized majority carriers from the photo-absorbing layer to the contact layer
Implementation Method 3
A photo-detector design featuring a photo-absorbing layer that is sensitive to the 3-5 μm wavelength range
Implementation Method 4
a generation current associated with the Shockley-Reed-Hall (SRH) process in the depletion region
Implementation Method 5
a diffusion current associated with auger or radiative processes in the extrinsic area
Implementation Method 6
a diffusion current associated with auger or radiative processes in the extrinsic area
Data Source
AI summary
A IDCA system with internal nBn photo-detector comprising: a photo-absorbing layer comprising an n-doped semiconductor exhibiting valence band energy level; a barrier layer, a first side of the barrier layer adjacent a first side of the photo-absorbing layer, the barrier layer exhibiting a valence band energy level substantially equal to the valence band energy level of the doped semiconductor of the photo absorbing layer; and a contact area comprising a doped semiconductor, the contact area being adjacent a second side of the barrier layer opposing the first side, the barrier layer exhibiting a thickness and conductance band gap sufficient to prevent tunneling of majority carriers from the photo-absorbing layer to the contact area, blocking the flow of thermalized majority carriers from the photo-absorbing layer to the contact area. Alternatively, a p-doped semiconductor is utilized, equalizing barrier conductance band energy levels and photo-absorbing layers.