Infrared Detector Light Confinement via Convex-Concave Structure
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Solution Overview
Problem
Infrared detectors face challenges in achieving high sensitivity, particularly for middle- and far-infrared bands, due to limitations in crystal growth, sensitivity to perpendicular light, and leakage issues, making it difficult to produce image sensors with both high sensitivity and a large number of pixels.
Innovation Solution
A light detector design featuring a convex-concave structure and a metal film on the outer circumferential face, which reflects and confines light within the detector, increasing effective optical path lengths and absorption efficiency, thereby enhancing sensitivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If HgCdTe is used for infrared detection, then detection sensitivity is improved, but manufacturing difficulty increases due to low melting point and high vapor pressure of Hg
Solution Approach 1:
The patent changes the material composition parameters by introducing Hg vacancies and adjusting the Hg content in HgCdTe, transforming the material from difficult-to-manufacture high-purity crystal to a controllable defective semiconductor material that maintains detection sensitivity while enabling easier fabrication
Solution Approach 2:
The patent employs a simple substrate structure (e.g., InP or InAs) that can be easily manufactured and discarded, replacing the need for complex high-quality crystal growth processes, thereby simplifying the manufacturing workflow while maintaining detection performance
2Ease of manufacture
If QWIP structure is used, then ease of manufacture is improved through well-established GaAs crystal-growth process, but detection sensitivity deteriorates due to one-dimensional electron quantization and lack of sensitivity to perpendicular light
Solution Approach 1:
The patent transitions from one-dimensional quantum well confinement to three-dimensional quantum dot confinement, enabling electrons to be quantized in all three spatial dimensions. This dimensional change creates discrete energy levels that are sensitive to perpendicular light incidence, fundamentally improving detection sensitivity while maintaining compatibility with GaAs-based manufacturing processes
3Measurement precision
If QDIP structure is used, then detection sensitivity is improved through three-dimensional electron confinement, but sensitivity remains lower than HgCdTe and manufacturing complexity increases
Solution Approach 1:
The patent introduces a type-II heterostructure as an intermediary system between quantum wells and quantum dots, using band alignment engineering to create effective three-dimensional confinement. This intermediary approach achieves quantum dot-like sensitivity while using simpler layer-by-layer growth processes, reducing manufacturing complexity compared to true quantum dot structures
4Productivity
If image sensor with large area and large number of pixels is produced, then productivity is improved, but detection sensitivity deteriorates due to difficulty in obtaining high-quality large-area substrates
Solution Approach 1:
The patent divides the large-area detector into multiple independent pixel elements that can be fabricated separately on standard-sized substrates and then integrated. This segmentation allows each pixel to maintain optimal detection sensitivity while the overall array achieves large area and high pixel count, solving the contradiction between scale and quality
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 configuration significantly improves sensitivity by extending optical paths and absorption efficiencies, achieving better performance compared to conventional QWIP and QDIP schemes, and enabling the production of high-sensitivity image sensors with a large number of pixels.
Implementation Method 1
a light confining structure including a convex-concave structure provided on a light acceptance surface and a metal film provided on an outer circumferential face of the light detector other than the light acceptance surface
Implementation Method 2
The light confining structure reflects and confines light within the detector, increasing effective optical path lengths
Implementation Method 3
Infrared detectors for middle- and far-infrared bands (for example, bands of wavelengths from 3 μm to 12 μm)
Data Source
Figure 1A~1B
Figure 2
Figure 3
AI summary
An infrared detector (10) which converts entering infrared IR into light in a different wavelength band, and which detects the converted light in the different wavelength band includes: a convex-concave structure (28) provided on a light acceptance surface of the infrared detector (10); and a metal film (24) provided on an outer circumferential face of the light detector (10) other than the light acceptance surface thereof, the metal film (24) covering the outer circumferential face. In the infrared detector (10), light which enters the light detector (10) after passing through the corvex-concave structure (28) and the converted light in the different wavelength band are confined inside the light detector (10): by causing the entering light to be reflected on the metal film (24) ; by causing light reflected on the metal film (24) to be reflected on the convex-concave structure (28); and by causing the converted light in the different wavelength band to be reflected between the metal film (24) and the convex-concave structure (28).