Light Receiving Device With Segmented Band Gap Layers
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Solution Overview
Problem
Light receiving devices for detecting near-infrared light face challenges in achieving high responsiveness and reducing dark current, particularly in applications like autonomous driving where low responsiveness can lead to incorrect detection of objects due to incomplete signal attenuation between reflected light pulses.
Innovation Solution
A light receiving device structure incorporating a substrate, a light receiving layer, an intermediate layer with a wider band gap than the light receiving layer, and a wide-gap layer with a pn junction, along with pixel isolation grooves, enhances responsiveness by facilitating hole movement and using a passivation film to prevent dark current increase.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If a conventional photodiode structure is used, then the device can detect near-infrared light, but the responsiveness is insufficient and signal attenuation is slow
Solution Approach 1:
The photodiode is divided into multiple functional layers with different band gaps: a light receiving layer (InGaAs) for detecting near-infrared light, an intermediate layer (InAlAs) with intermediate band gap, and a wide-gap layer (InP) for hole suppression. This segmentation allows each layer to perform its specific function optimally, achieving both high responsiveness and complete signal attenuation.
Solution Approach 2:
Different regions of the device have different material compositions and band gap properties tailored to local requirements. The light receiving layer has a narrow band gap for high quantum efficiency, while the wide-gap layer has a large band gap to suppress dark current and enable fast signal attenuation. This local optimization resolves the contradiction between responsiveness and signal attenuation.
2Use of energy by moving object
If the band gap of the light receiving layer is reduced to improve quantum efficiency, then more near-infrared light can be detected, but dark current increases
Solution Approach 1:
An intermediate layer with band gap between the light receiving layer and wide-gap layer is introduced as a mediator. This intermediate layer (InAlAs) provides a gradual transition in band gap, facilitating carrier transport while maintaining the low dark current特性 of the wide-gap layer. This resolves the contradiction by allowing the light receiving layer to have narrow band gap for high quantum efficiency while the intermediate and wide-gap layers suppress dark current.
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 device exhibits improved responsiveness with faster signal attenuation and reduced dark current, enabling accurate detection of near-infrared light, particularly in applications like autonomous driving.
Implementation Method 1
a photodiode may use a III-V compound semiconductor as a light receiving layer for absorbing near-infrared light
Implementation Method 2
a wide-gap layer having a pn junction disposed on the intermediate layer
Data Source
AI summary
A light receiving device includes a substrate, a first contact layer disposed on a surface of the substrate, a light receiving layer disposed on the first contact layer, an intermediate layer disposed on the light receiving layer, a wide-gap layer having a pn junction disposed on the intermediate layer, a second contact layer disposed on the wide-gap layer, and a groove formed for pixel isolation by removing the second contact layer and part of the wide-gap layer, wherein the intermediate layer has a wider band gap than the light receiving layer, and wherein the wide-gap layer has a wider band gap than the intermediate layer.