Type-II Quantum-Well Photodetector Structure for Lower Dark Current
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Solution Overview
Problem
Conventional light receiving elements with type-II quantum-well layers experience increased crystal leakage during the formation of an antireflective film, leading to elevated dark current, which is not effectively addressed by existing technologies.
Innovation Solution
Incorporating a light receiving element with a substrate having a type-II quantum-well layer and a second semiconductor layer with an AlxGayIn1-x-yAs layer, where 0≤x<1, 0≤y<1, and 0<x+y<1, and an n-type region with a high concentration of n-type carriers below the groove's bottom surface, which suppresses crystal leakage and reduces dark current.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a type-II quantum-well layer is used in the light receiving element, then the sensitivity in the wavelength range of 1.0 μm to 2.5 μm is improved, but crystal leakage increases during antireflective film formation, leading to elevated dark current
Solution Approach 1:
An n-type region is formed in advance at the bottom surface of the groove before antireflective film formation. This preliminary action ensures that when crystal leakage occurs during subsequent antireflective film formation, the pre-formed n-type region suppresses the leakage, preventing dark current elevation while maintaining the sensitivity benefits of the type-II quantum-well layer.
Solution Approach 2:
The n-type region acts as an intermediary layer between the type-II quantum-well layer and the groove bottom surface. It mediates the harmful crystal leakage effect by providing a high concentration of n-type carriers that suppress leakage paths, thereby protecting the light receiving element from dark current increase while preserving the quantum-well layer's sensitivity.
2Reliability
If grooves for pixel separation are formed deeply to separate pixels, then pixel isolation is improved, but crystal leakage paths increase, leading to higher dark current
Solution Approach 1:
The n-type region is locally formed at the bottom surface of the groove where crystal leakage most critically occurs. This localized quality enhancement provides targeted suppression of leakage paths at the most vulnerable point, maintaining pixel isolation benefits while specifically addressing the dark current issue at the groove bottom.
Solution Approach 2:
The n-type region is formed in advance to counteract the harmful crystal leakage effect that will occur during and after groove formation. This preliminary anti-action creates a protective region that neutralizes the leakage paths created by deep grooves, allowing effective pixel isolation without the penalty of elevated dark current.
3Object-generated harmful factors
If the concentration of n-type carriers is increased to suppress crystal leakage, then dark current is reduced, but the device complexity increases
Solution Approach 1:
The light receiving element is segmented into distinct functional regions: the type-II quantum-well layer for light detection, the n-type region for leakage suppression, and the groove structure for pixel separation. This segmentation allows each component to perform its specific function efficiently, achieving dark current reduction through the dedicated n-type region without complicating the overall device architecture.
Solution Approach 2:
The n-type region serves as an intermediary component that specifically addresses crystal leakage without requiring fundamental changes to the light receiving element's core structure. By introducing this single intermediate layer at the groove bottom surface, dark current is reduced while maintaining the simplicity of the overall device design.
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 by maintaining a high concentration of n-type carriers, even after the formation of the antireflective film, thereby improving the signal-to-noise ratio and sensitivity in the wavelength range of 1.0 μm to 2.5 μm.
Implementation Method 1
a type-II quantum-well layer including an InGaAs layer and a GaAsSb layer
Implementation Method 2
an n-type region with a high concentration of n-type carriers below the groove's bottom surface, which suppresses crystal leakage and reduces dark current
Implementation Method 3
The second semiconductor layer includes a AlxGayIn1-x-yAs layer, where 0≤x<1, 0≤y<1, and 0<x+y<1
Data Source
AI summary
A light receiving element includes a substrate having a first main surface, and includes a light receiving layer provided on the first main surface. The light receiving layer includes a first semiconductor layer and a second semiconductor layer provided on the first semiconductor layer. The light receiving element includes a contact layer provided on the light receiving layer, and includes a groove that separates the contact layer for each pixel. The first semiconductor layer includes a type-II quantum-well layer including an InGaAs layer and a GaAsSb layer. The second semiconductor layer includes a AlxGayIn1-x-yAs layer, where 0≤x<1, 0≤y<1, and 0<x+y<1. The bottom surface of the groove is situated between a top surface and a bottom surface of the second semiconductor layer, and the light receiving layer includes an n-type region below an exposed portion of a bottom surface of the groove.