Barrier-Layer Infrared Photodetector for Low Dark Current
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Solution Overview
Problem
Existing infra-red detectors require cooling to cryogenic temperatures to reduce dark current, which is costly and limits their operational temperature and durability.
Innovation Solution
A photo-detector design featuring a photo-absorbing layer, a barrier layer with a sufficient thickness and band gap to block majority carriers, and a contact layer, which allows for operation without a depletion layer and reduces dark current.
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 invention extracts and eliminates the need for cryogenic cooling systems by redesigning the photodetector structure. The barrier layer is specifically designed to block majority carriers while allowing minority carriers to pass, thereby reducing dark current generation at the source without requiring external cooling mechanisms.
Solution Approach 2:
The invention changes the operational temperature parameter from cryogenic ranges to higher temperatures. By modifying the barrier layer thickness and band gap characteristics, the photodetector achieves low dark current performance at elevated temperatures where conventional devices would fail, eliminating the need for cooling systems.
2Object-generated harmful factors
If passivation layers are added to reduce surface current, then surface current is reduced, but manufacturing complexity and cost increase
Solution Approach 1:
The invention removes the need for separate passivation layers by integrating surface current blocking functionality directly into the barrier layer structure. The barrier layer is designed with specific thickness and material properties that simultaneously block majority carriers in the bulk and prevent surface current generation at interfaces.
Solution Approach 2:
The invention merges the functions of the barrier layer and passivation layer into a single integrated structure. The barrier layer performs both bulk carrier blocking and surface passivation functions, eliminating the need for additional passivation process steps and reducing manufacturing complexity.
3Object-generated harmful factors
If barrier layer thickness is increased to block majority carriers, then dark current is reduced, but minority carrier transmission may be affected
Solution Approach 1:
The invention applies local quality by creating a spatially varying barrier structure with different characteristics at different locations. The barrier layer has optimized thickness and material composition that provides strong blocking for majority carriers in the bulk region while maintaining sufficient transparency for minority carriers at the interface regions where they are generated and collected.
Solution Approach 2:
The invention optimizes the barrier layer parameters (thickness, material composition, band gap) to achieve selective carrier blocking. By carefully tuning these parameters, the barrier becomes sufficiently thick to prevent majority carrier tunneling while remaining thin enough or having appropriate band alignment to allow minority carrier transmission through thermionic emission or diffusion mechanisms.
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 and eliminates the need for passivation, enabling the photo-detector to operate at higher temperatures and reducing power consumption and weight.
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-absorbing layer, preferably exhibiting a thickness on the order of the optical absorption length
Implementation Method 4
The SRH generation process is very efficient in the depletion region of photodiodes where the mid-gap traps are highly activated. It is the main source of the dark current in photodiodes operable for mid-wavelength infrared at temperatures below 200K
Data Source
AI summary
A camera having an integrated dewar cooler assembly (IDCA) with an optical window, and a reduced dark current photodetector disposed within the IDCA to receive light passing through the optical window. The photodetector comprising a semiconductor photo absorbing layer, a semiconductor barrier layer having a thickness and a first side adjacent a 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 photo absorbing layer and a conduction band energy level exhibiting an energy gap in relation to the conduction band of the photo absorbing layer, and a contact area comprising a doped semiconductor, the contact area is adjacent a second side of the barrier layer opposing the first side. The energy gap and/or the thickness of the of the barrier layer is sufficient to minimize charge carriers tunneling and thermalization.