Type II MQW Photodiode Responsivity Optimization
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Solution Overview
Problem
The responsivity of photodiodes with a type II InGaAs/GaAsSb multiple quantum well (MQW) structure is high on long wavelengths but drops significantly at shorter wavelengths, such as 1.5 μm, leading to undesirable spectral analysis results, and existing designs struggle to maintain consistent responsivity across the entire wavelength region.
Innovation Solution
A photodiode with a type II MQW structure featuring 50 or more pairs of group III-V compound semiconductor layers, where the thickness of the layer with a higher valence band potential is reduced, maintaining the thickness of the layer with a lower valence band potential, to enhance electron and hole movement and apply a reverse bias voltage to increase the electric field intensity, thereby improving responsivity across the entire wavelength region.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the number of MQW pairs is increased to improve long wavelength absorption, then device complexity increases
Solution Approach 1:
The patent applies parameter changes by optimizing the thickness parameters of the individual layers within each MQW pair. By carefully selecting the thickness of the first layer (with higher valence band potential) to be thinner than the second layer, the structure achieves improved carrier transport and flattened responsivity across the wavelength region without requiring an excessive number of MQW pairs, thus controlling device complexity.
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 achieves flat or gently varying responsivity across the wavelength region, particularly improving responsivity on the short wavelength side, while maintaining high responsivity on the long wavelength side, and reducing the disappearance of holes, thus preventing a drop in responsivity.
Implementation Method 1
when light absorption occurs in an absorption layer, electrons in the valence band are excited up to the conduction band, and holes are generated in the valence band
Implementation Method 2
apply a reverse bias voltage to increase the electric field intensity, thereby improving responsivity
Data Source
AI summary
A photodiode and the like capable of preventing the responsivity on the short wavelength side from deteriorating while totally improving the responsivity in a type II MQW structure, is provided. The photodiode is formed on a group III-V compound semiconductor substrate, and includes a pixel. The photodiode includes an absorption layer of a type II MQW structure, which is located on the substrate. The MQW structure includes fifty or more pairs of two different types of group III-V compound semiconductor layers. The thickness of one of the two different types of group III-V compound semiconductor layers, which layer has a higher potential of a valence band, is thinner than the thickness of the other layer.