Avalanche Photodetector Charge Sheet Thickness Control
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Solution Overview
Problem
Current avalanche photodetectors face challenges in reducing dark current and enhancing gain, particularly in the design of multiplication and absorption regions, which affects their sensitivity and performance.
Innovation Solution
A vertically-stacked structure for an avalanche photodetector is developed, featuring a charge sheet with varying thickness and a multiplication region with corrugations, positioned between the absorption and multiplication regions, to control the electric field and enhance signal amplification.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If a conventional avalanche photodetector structure is used, then the device is simpler to manufacture, but dark current is higher and gain is reduced
Solution Approach 1:
The photodetector structure is divided into distinct functional regions: a multiplication region with a first semiconductor layer and an absorption region with a second semiconductor layer. This segmentation allows independent optimization of each region's properties to reduce dark current while maintaining manufacturing feasibility
Solution Approach 2:
Different semiconductor layers are used with specific properties optimized for their local function: the first layer (multiplication region) is designed for carrier multiplication with specific thickness and doping, while the second layer (absorption region) is optimized for photon absorption. This local quality differentiation reduces dark current by ensuring each region performs its specific function efficiently
2Power
If a conventional avalanche photodetector structure is used, then the device is simpler to manufacture, but gain is reduced
Solution Approach 1:
The device is segmented into a multiplication region and an absorption region, allowing the multiplication region to be specifically engineered for high gain through controlled avalanche breakdown, while the absorption region focuses on efficient photon detection. This segmentation enables gain enhancement without requiring complete structural redesign
Solution Approach 2:
The thickness of the first semiconductor layer in the multiplication region is optimized to control the electric field distribution and avalanche multiplication efficiency. By adjusting this parameter, gain is enhanced while maintaining a manageable structural complexity
3Measurement precision
If the thickness of semiconductor layers is increased, then sensitivity is improved, but bandwidth is reduced
Solution Approach 1:
The thickness of the first semiconductor layer in the multiplication region is optimized to balance sensitivity and bandwidth. A thinner multiplication region improves bandwidth by reducing carrier transit time, while still providing sufficient multiplication gain. The second semiconductor layer thickness is optimized for photon absorption efficiency, improving sensitivity without excessively increasing total device thickness
Solution Approach 2:
The patent introduces a vertically stacked configuration with distinct functional layers, allowing independent optimization of thickness parameters for each layer. This dimensional arrangement enables sensitivity improvement through adequate absorption path length while maintaining bandwidth through controlled multiplication region thickness
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 reduces dark current and provides gain enhancement compared to conventional designs, allowing for improved sensitivity and adjustable bandwidth through the optimized thickness of semiconductor layers.
Implementation Method 1
The charge sheet has a thickness that varies with position in a horizontal plane, and the charge sheet is positioned in the vertical direction between the second semiconductor layer and the first portion of the first semiconductor layer
Implementation Method 2
By applying a high reverse bias voltage that is less than the breakdown voltage, an avalanche photodetector exhibits an internal current gain effect because of impact ionization that produces an avalanche effect
Implementation Method 3
an avalanche photodetector exhibits an internal current gain effect because of impact ionization that produces an avalanche effect
Implementation Method 4
An avalanche photodetector, also known as an avalanche photodiode, is a highly-sensitive semiconductor photodetector that relies upon the photoelectric effect to convert light into countable current pulses
Data Source
AI summary
Structures for an avalanche photodetector and methods of forming a structure for an avalanche photodetector. The structure includes a first semiconductor layer having a first portion and a second portion, and a second semiconductor layer stacked in a vertical direction with the first semiconductor layer. The first portion of the first semiconductor layer defines a multiplication region of the avalanche photodetector, and the second semiconductor layer defines an absorption region of the avalanche photodetector. The structure further includes a charge sheet in the second portion of the first semiconductor layer. The charge sheet has a thickness that varies with position in a horizontal plane, and the charge sheet is positioned in the vertical direction between the second semiconductor layer and the first portion of the first semiconductor layer.