Infrared Detector Absorber Segmentation for Carrier Collection

Resolve Bottlenecks,
Find Innovative SolutionsGenerate Solutions

Solution Overview

Problem

Infrared detectors face reduced quantum efficiency due to absorber thickness exceeding minority carrier diffusion length, leading to increased recombination and reduced collection of minority carriers.

Innovation Solution

The use of two absorber layers separated by a collector, with each absorber's thickness being less than the minority carrier diffusion length, and electrically connecting the absorbers and barriers in parallel to enhance the collection of minority carriers upon receiving an infrared flux.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Productivity

If the absorber thickness is increased to improve photon absorption probability, then quantum efficiency is improved, but minority carrier recombination increases and carrier collection is reduced

Engineering Contradiction:

Improvequantum efficiencyVSAvoidminority carrier collection

Core Design Contradiction:

ProductivityVSReliability

Solution Approach 1:

The single thick absorber is segmented into multiple thinner absorber layers (first absorber, second absorber, etc.) separated by collector layers. Each absorber layer has a thickness less than the minority carrier diffusion length, ensuring that carriers generated in each layer can reach the collector before recombining. This segmentation resolves the contradiction by maintaining high photon absorption probability through multiple layers while keeping each layer thin enough for effective carrier collection.

Inventive Principle:

Principle #1Segmentation

2Quantity of substance

If a single thick absorber is used to maximize photon absorption, then quantum efficiency improves, but the diffusion length is exceeded and recombination increases

Engineering Contradiction:

Improveabsorber material thicknessVSAvoidcarrier recombination loss

Core Design Contradiction:

Quantity of substanceVSLoss of energy

Solution Approach 1:

The total absorber material is divided into multiple segments (first absorber, second absorber, third absorber) with intermediate collector layers. Each segment has optimized thickness below the diffusion length threshold, preventing carrier recombination while collectively providing sufficient material for high photon absorption. This segmentation allows the system to achieve both high absorber quantity and low recombination loss.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Collector layers are introduced as intermediary structures between the absorber layers. These collectors serve as intermediate collection points that capture minority carriers from adjacent absorber layers before they can recombine. The intermediaries (collectors) enable the system to use thicker total absorber material while maintaining low recombination losses through staged carrier collection.

Inventive Principle:

Principle #24Intermediary (Mediator)

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 increases the probability of photon absorption and improves quantum efficiency by ensuring minority carriers are collected without recombination, thereby enhancing the detection capability of infrared detectors.

Implementation Method 1

The infrared detector receives an infrared flux that includes photons that are absorbed by the absorber

Methodology Applied

Scientific EffectAbsorption (EM radiation): Absorption (EM radiation)

Implementation Method 2

When a photon is absorbed, the energy of the photon is transferred to an electron, causing the electron to rise from the valence band to the conduction band, leaving a hole in the valence band, thereby creating an electron-hole pair

Methodology Applied

Scientific EffectPhotoelectric Effect: Photoelectric Effect

Implementation Method 3

the majority carrier is blocked from reaching the collector by the barrier

Methodology Applied

Scientific EffectElectrical Resistance: Electrical Resistance

Implementation Method 4

In response to a voltage being applied to the collector, the first and second set of minority carriers are collected at the collector

Methodology Applied

Scientific EffectElectrical Conduction: Conduction (electrical)

Data Source

PatentUS11598673B2Infrared detecting with multiple absorbers in a sensing element

Publication Date: 2023.03.07 RAYTHEON CO

AI summary

A sensing element of an infrared detector including a first absorber configured to form a first set of minority carriers upon receipt of an infrared flux, a collector, a first barrier disposed between the first absorber and the collector, a second absorber configured to form a second set of minority carriers upon receipt of the infrared flux, and a second barrier disposed between the second absorber and the collector. In response to a voltage being applied to the collector, the first and second set of minority carriers are collected at the collector.