InP-Capped InGaAs Photodetectors With Lower Dark Current
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Solution Overview
Problem
Conventional photodetectors with InGaAs lattice-matched to InP face challenges in achieving low dark current due to lateral diffusion, which limits their sensitivity and performance in hyper spectral imaging applications.
Innovation Solution
A method involving the epitaxial growth of an InP cap layer on an InGaAs absorption region layer, followed by precise dry etching to reduce the InP cap layer thickness to nanometer ranges, combined with dielectric passivation and anti-reflective coatings, to minimize lateral diffusion and enhance sensitivity to visible light wavelengths.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If the InP cap layer thickness is reduced to minimize lateral diffusion, then dark current is reduced, but surface quality and light admission may deteriorate
Solution Approach 1:
The patent applies parameter changes by precisely controlling the InP cap layer thickness to a specific range (50-200 nm) and using controlled dry etching processes to achieve the desired thickness reduction while maintaining surface quality. This resolves the contradiction by finding the optimal parameter range that minimizes lateral diffusion without compromising surface integrity
Solution Approach 2:
The patent replaces traditional mechanical polishing methods with dry etching processes to thin the InP cap layer. This substitution allows for more precise control over thickness and better surface quality preservation, as dry etching can achieve atomic-level precision without the mechanical stresses that would compromise surface integrity
2Measurement precision
If the InP cap layer thickness is reduced to enhance visible light sensitivity, then quantum efficiency improves, but dark current reduction may compromise structural integrity
Solution Approach 1:
The patent changes the thickness parameter of the InP cap layer to a specific range (50-200 nm) that allows visible light to pass through while maintaining sufficient material to preserve structural integrity. This optimal parameter range enables enhanced sensitivity without compromising the mechanical strength of the detector structure
Solution Approach 2:
The patent uses a composite layered structure combining InP cap layer with InGaAs absorption region and InP substrate. This composite approach allows each layer to perform its specific function - the thin InP cap for visible light transmission while the underlying layers provide structural support and infrared absorption, resolving the contradiction between sensitivity enhancement and structural integrity
3Ease of manufacture
If conventional etching methods are used to thin the InP cap layer, then manufacturing is simpler, but surface quality and control precision deteriorate
Solution Approach 1:
The patent replaces conventional wet etching or mechanical polishing with dry etching processes. This substitution provides superior thickness control precision and surface quality while remaining manufacturable through established semiconductor fabrication techniques. The dry etching process offers anisotropic etching that precisely controls thickness without compromising surface integrity
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 approach significantly reduces dark current and improves sensitivity to visible light wavelengths, enabling wide bandwidth hyper spectral imaging with enhanced quantum efficiency and spectral response, while maintaining surface quality comparable to epitaxial growth.
Implementation Method 1
growing the InP cap layer epitaxially on the InGaAs absorption region layer
Implementation Method 2
removing a portion of the InP cap layer by dry etching
Implementation Method 3
Dry etching can include ICP etching. The ICP can be a chlorine free process.
Implementation Method 4
Lateral diffusion in the cap increases the junction area and thus increases dark current
Implementation Method 5
sensitivity down into visible light wavelengths for hyper spectral imaging
Data Source
AI summary
A method includes forming an assembly of layers including an InP cap layer on an InGaAs absorption region layer, wherein the InGaAs layer is on an n-InP layer, and wherein an underlying substrate layer underlies the n-InP layer. The method includes removing a portion of the InP cap and n-InP layer by dry etching.