InGaAs Photodetector Array with Type-II MQW and Selective Diffusion
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Solution Overview
Problem
InGaAs photodetectors for near-infrared light have high dark current due to non-lattice-matched InGaAs absorption layers, leading to increased noise and the need for cooling, and lack sensitivity in the 1-1.5 μm range when using InAsP window layers, with no reported examples of light receiving element arrays or sensitivity measurements.
Innovation Solution
A light receiving element array with a type-II multi-quantum well structure and a p-type region extending from the contact layer to the n-type buffer layer, formed by selective diffusion of a p-type impurity, which reduces the energy barrier for hole movement and increases sensitivity, allowing for high sensitivity in the near-infrared region without the need for cooling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If InGaAs absorption layer is used for near-infrared detection, then sensitivity in near-infrared region is improved, but dark current increases due to non-lattice-matched structure
Solution Approach 1:
An InAlAs buffer layer is introduced between the InP substrate and the InGaAs absorption layer. This buffer layer serves as an intermediary that gradually transitions the lattice structure, reducing misfit dislocations and minimizing dark current while preserving the high sensitivity of the InGaAs absorption layer for near-infrared detection.
Solution Approach 2:
The composition ratio of Al in the InAlAs buffer layer is optimized to balance two competing requirements: sufficient Al content to provide lattice matching and reduce misfit dislocations (lowering dark current), while limiting Al content to maintain high light-reception sensitivity. This parameter optimization resolves the contradiction between reducing dark current and maintaining sensitivity.
2Object-generated harmful factors
If InAsP window layer is used to achieve lattice matching, then dark current is reduced, but sensitivity in 1-1.5 μm wavelength range decreases
Solution Approach 1:
The InAlAs buffer layer acts as an intermediary between the InP substrate and InGaAs absorption layer, providing lattice matching without introducing the absorption band problem that affects InAsP window layers. This allows the device to maintain high sensitivity in the 1-1.5 μm range while still achieving low dark current through proper lattice matching.
3Measurement precision
If cooling device is added to reduce noise from dark current, then S/N ratio is improved, but device size and complexity increase
Solution Approach 1:
The patent converts the harmful effect of lattice mismatch into a benefit by deliberately designing an InAlAs buffer layer with controlled composition. This buffer layer transforms the potential harm of lattice mismatch (which would increase dark current) into a solution that reduces misfit dislocations and lowers dark current, thereby improving S/N ratio without requiring cooling devices.
4Measurement precision
If p-type region extends deep into buffer layer, then hole collection efficiency is improved, but manufacturing precision requirements increase
Solution Approach 1:
The diffusion depth of the p-type region is optimized to extend into the InAlAs buffer layer but stop before reaching the InP substrate. This parameter control allows efficient hole collection from the absorption layer while preventing excessive diffusion that would compromise manufacturing precision and device performance.
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 achieves high light-reception sensitivity in both substrate and contact layer illuminations, reducing dark current and enabling accurate detection of biological components with improved crystal quality and reduced noise.
Implementation Method 1
A light receiving element array, in which a plurality of light receiving elements are arranged on a substrate (1) composed of a compound semiconductor, is used. The light receiving element array includes an n-type buffer layer (2) disposed on the substrate (1), an absorption layer (3) disposed on the n-type buffer layer (2) and having a type-II multi-quantum well structure
Implementation Method 2
a p-type region (6) that is provided for each of the light receiving elements and that extends from a surface of the contact layer (5) to the n-type buffer layer (2) through the absorption layer (3). The p-type region (6) is formed by selectively diffusing a p-type impurity
Data Source
AI summary
The present invention provides a light receiving element array etc., having a high light-reception sensitivity in the near-infrared region, an optical sensor device, and a method for producing the light receiving element array. A light receiving element array 55 includes an n-type buffer layer 2 disposed on an InP substrate 1, an absorption layer 3 having a type-II MQW, a contact layer 5 disposed on the absorption layer, and a p-type region extending to the n-type buffer layer 2 through the absorption layer 3, wherein the p-type region formed by selective diffusion is separated from the p-type region of an adjacent light receiving element by a region that is not subjected to selective diffusion, and, in the n-type buffer layer, a p-n junction 15 is formed on a crossed face of a p-type carrier concentration of the p-type region and an n-type carrier concentration of the buffer layer.