Infrared Detector Barrier Layer Valence Band Alignment

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Solution Overview

Problem

Existing infrared detectors face limitations in accurately detecting radiation across multiple spectral bands due to misalignment of valence band energy levels in barrier and absorption layers, which can lead to increased dark current and reduced performance when using bias voltages greater than 500 mV, especially with silicon-based readout integrated circuits.

Innovation Solution

The use of an alloy comprising aluminum and antimony, and at least one of gallium or arsenic, for the barrier layer, which is selected to align valence bands with absorption layers sensitive to both short and medium wavelength infrared spectral bands, allowing for concurrent detection without the need for lattice matching and enabling operation at near 0 volt bias.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of manufacture

If a uniform barrier layer is used with an absorption layer, then the detector structure is simple to fabricate, but the valence band energy levels are misaligned when used with a second absorption layer sensitive to a different wavelength band

Engineering Contradiction:

Improvefabrication simplicityVSAvoidcompatibility with multiple absorption layers

Core Design Contradiction:

Ease of manufactureVSAdaptability or versatility

Solution Approach 1:

The barrier layer is designed with a compositional gradient, transitioning from a first composition near the first absorption layer to a second composition near the second absorption layer. This local variation in material composition allows each region of the barrier layer to be optimized for alignment with its adjacent absorption layer, enabling compatibility with multiple spectral bands while maintaining a single continuous layer structure

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The barrier layer composition is varied by changing the ratio of group III elements (gallium, indium, aluminum) and group V elements (arsenic, antimony) across the layer thickness. This parameter change in chemical composition directly controls the valence band edge alignment with different absorption layers sensitive to different infrared wavelength bands

Inventive Principle:

Principle #35Parameter changes

2Reliability

If a bias voltage greater than 500 mV is applied to remedy valence band misalignment, then the detector performance improves, but the dark current increases and reduces detection accuracy

Engineering Contradiction:

Improvedetector performanceVSAvoiddark current

Core Design Contradiction:

ReliabilityVSObject-generated harmful factors

Solution Approach 1:

The barrier layer composition is pre-configured with a gradient designed to achieve proper valence band alignment with multiple absorption layers. This preliminary structural design eliminates the need for high bias voltages to remedy misalignment, allowing the detector to operate at low bias voltages (below 500 mV) while maintaining high performance and low dark current

Inventive Principle:

Principle #10Preliminary action

3Measurement precision

If a bias voltage greater than 500 mV is applied to align energy levels, then the detection accuracy improves, but the internal bias circuitry in silicon-based readout integrated circuits cannot supply the required voltage

Engineering Contradiction:

Improveinfrared radiation detection accuracyVSAvoidbias voltage compatibility with readout circuitry

Core Design Contradiction:

Measurement precisionVSEase of operation

Solution Approach 1:

The barrier layer is pre-engineered with a compositional gradient that establishes proper valence band alignment with multiple absorption layers. This preliminary design ensures that the detector can achieve high measurement precision while operating at low bias voltages that are compatible with the internal bias circuitry of silicon-based readout integrated circuits

Inventive Principle:

Principle #10Preliminary action

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 solution enables efficient detection of infrared radiation across multiple spectral bands with reduced dark current and improved performance, allowing for accurate detection of both short and medium wavelength radiation without the limitations imposed by high bias voltages.

Implementation Method 1

the composition of the alloy is selected such that valence bands of the absorption layer and the barrier layer substantially align

Methodology Applied

Scientific EffectValence band alignment:

Data Source

PatentUS9923114B2Infrared detector and method of detecting one or more bands of infrared radiation

Publication Date: 2018.03.20 THE BOEING CO

AI summary

An infrared detector is provided. The infrared detector includes an absorption layer sensitive to radiation in only a short wavelength infrared spectral band, and a barrier layer coupled to the absorption layer. The barrier layer is fabricated from an alloy including aluminum and antimony, and at least one of gallium or arsenic, and the composition of the alloy is selected such that valence bands of the absorption layer and the barrier layer substantially align.