Mesa Infrared Detector Passivation for Low Leakage Current

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Solution Overview

Problem

Infrared detecting devices face challenges in achieving high signal noise ratio (SNR) characteristics due to high intrinsic carrier density and low device resistance, leading to increased leakage currents, especially in semiconductor materials with small bandgaps.

Innovation Solution

The design incorporates a semiconductor substrate with a mesa structure formed by layers of AlxIn1-xSb, where the light receiving layer contains 0.05<x<0.18, and the side surfaces are covered with a protective silicon nitride layer, enhancing device resistance and reducing recombination currents.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If semiconductor materials with small bandgaps are used for detecting infrared rays of wavelength 2 μm or more, then the detecting capability for long wavelength infrared is improved, but the intrinsic carrier density increases and device resistance decreases, leading to high leakage currents and poor PN diode characteristics

Engineering Contradiction:

Improveinfrared detecting capabilityVSAvoidPN diode characteristics

Core Design Contradiction:

Adaptability or versatilityVSReliability

Solution Approach 1:

The invention changes the material composition parameter by using AlInSb compound semiconductor with specific aluminum composition ratio (0.05 < x < 0.18) to optimize the bandgap and carrier density, achieving both long-wavelength infrared detection capability and sufficient PN diode characteristics at room temperature

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The invention uses composite AlInSb compound semiconductor material combining aluminum, indium, and antimony elements to create a layered structure with different bandgaps, enabling both high quantum efficiency for long-wavelength infrared and controlled electrical characteristics

Inventive Principle:

Principle #40Composite materials

2Reliability

If cooling mechanisms are added to suppress thermally excited carriers, then the leakage current is reduced and PN diode characteristics improve, but the device complexity and size increase

Engineering Contradiction:

Improveleakage current suppressionVSAvoiddevice structure

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The invention converts the harmful thermal excitation effect into a beneficial feature by designing the AlInSb bandgap structure such that the narrow bandgap enables room-temperature operation while the specific material composition suppresses thermal carrier generation, eliminating the need for cooling mechanisms

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

3Reliability

If the aluminum composition ratio in the light receiving layer is increased to improve device resistance, then the leakage current decreases, but the quantum efficiency and photocurrent generation capability are reduced

Engineering Contradiction:

Improvedevice resistanceVSAvoidphotocurrent

Core Design Contradiction:

ReliabilityVSPower

Solution Approach 1:

The invention optimizes the aluminum composition ratio parameter within the specific range (0.05 < x < 0.18) to achieve the best balance between device resistance and quantum efficiency, where the lower bound ensures sufficient photocurrent while the upper bound maintains adequate device resistance

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The invention uses a small but precise amount of aluminum composition (not zero, but limited to specific range) to achieve the necessary device resistance improvement without excessively compromising the quantum efficiency, finding the optimal partial concentration

Inventive Principle:

Principle #16Partial or excessive 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 configuration improves the signal noise ratio (SNR) of infrared detecting devices by increasing device resistance without lowering photocurrent, thereby enhancing the overall performance.

Implementation Method 1

electrons and holes generated by the absorbed infrared rays in a light receiving layer

Methodology Applied

Scientific EffectPhotoelectric effect: Photoelectric Effect

Implementation Method 2

the side surfaces are covered with a protective silicon nitride layer, enhancing device resistance and reducing recombination currents

Methodology Applied

Scientific EffectSurface passivation:

Data Source

PatentUS12002897B2Infrared detecting device

Publication Date: 2024.06.04 ASAHI KASEI MICRODEVICES CORP

AI summary

An infrared detecting device is provided. The infrared detecting device includes: a semiconductor substrate; a first layer having a first conductivity type on the semiconductor substrate; a light receiving layer on the first layer; and a second layer having a second conductivity type on the light receiving layer. A part of the first layer, the light receiving layer, and the second layer form a mesa structure. The second layer contains AlzIn1-zSb (0.05<z<0.18). The side surfaces and an upper surface of the mesa structure are covered with the protective layer. A part of an upper surface of the second layer that forms an interface between the second layer and the protective layer has an oxide layer made of a constituent material of the second layer. The oxide layer includes an oxide of Al and has no oxide of Sb.