Light Absorber Array Layout for Higher Detector Responsivity
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Solution Overview
Problem
Free space light detectors with thin film absorption layers have low responsivity due to their thickness being substantially smaller than the wavelength of light they are intended to detect, leading to inadequate light absorption and low current generation.
Innovation Solution
Employing an array of light absorption regions on a semiconductor substrate with specific dimensions and materials tailored to the target wavelength, enhancing light absorption through destructive interference and cavity formation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a thin film light absorption layer is used, then the device structure is simple and manufacturing is easier, but the light absorption capability is insufficient leading to low responsivity
Solution Approach 1:
The continuous light absorption layer is segmented into an array of discrete light absorption regions (pillars, posts, or rods) with lateral dimensions between 0.5-10 micrometers. This segmentation creates multiple interfaces that trap light through total internal reflection, significantly enhancing the absorption path length and light harvesting efficiency while maintaining a thin film structure that is easy to manufacture.
Solution Approach 2:
The invention transitions from a two-dimensional continuous layer to a three-dimensional array structure with vertical pillars extending from the substrate. This dimensional change creates additional light-trapping interfaces and increases the effective absorption volume within the same footprint, improving responsivity without compromising manufacturing simplicity.
2Reliability
If the absorption layer thickness is increased to improve light absorption, then light absorption capability improves, but the thickness becomes comparable to the wavelength of light which complicates the device structure
Solution Approach 1:
Instead of increasing the continuous layer thickness, the invention segments the absorption material into discrete vertical pillars. The lateral dimensions of these pillars (0.5-10 micrometers) are kept much smaller than the light wavelength, avoiding the problem of thickness comparable to wavelength while creating multiple light-trapping interfaces that enhance absorption efficiency.
Solution Approach 2:
The invention applies light-trapping structures locally at the pillar-substrate interfaces and pillar-air interfaces, concentrating the light absorption enhancement at specific locations rather than uniformly increasing the overall thickness. This localized approach improves responsivity without requiring the entire structure to be thick.
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 array configuration significantly increases light absorption and current production, resulting in higher responsivity compared to continuous absorption layers.
Implementation Method 1
A free space light detector can include a light absorption layer in which electron-hole pairs can be created as a result of photons of light entering the absorption layer
Implementation Method 2
enhancing light absorption through destructive interference and cavity formation
Data Source
AI summary
A device includes a semiconductor substrate having a surface. The device includes a first region in the substrate having a first dopant, a second region in the substrate having a second dopant, and a third region in the substrate having the first dopant. A first light absorption layer is on the surface and over a fourth region of the substrate between the first and second regions. The first light absorption layer is configured to absorb light of a particular wavelength. A second light absorption layer is on the surface and over a fifth region of the substrate between the second and third regions. The second light absorption layer is configured to absorb the light of the particular wavelength. At least one of lateral dimensions of the first and second light absorption layers or a lateral separation between the first and second light absorption layers is based on the particular wavelength.