Avalanche Photodiode Structure for Hyperfrequency Bandwidth
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Solution Overview
Problem
Avalanche photodiodes currently have limited bandwidth, making them unsuitable for receiving optical signals modulated in the hyperfrequency range, particularly those above 10 GHz, due to restricted response time and gain limitations.
Innovation Solution
The design of an avalanche photodiode structure with specific semiconducting zones optimized for carrier multiplication and absorption, featuring a first zone for radiation reception, a multiplication zone with preponderant electron impact ionization, and a collection zone with a higher electron concentration, creating an electric field in the third zone for accelerated electron drift without multiplication, enhancing bandwidth and response time.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If additional layers are integrated upstream and downstream from the absorption layer to accelerate carrier injection, then response time is improved and bandwidth is increased, but gain is limited and cannot achieve genuine significant gains above 10 GHz
Solution Approach 1:
The multiplication zone is segmented into a first portion and a second portion, with the first portion providing electron preponderant multiplication and the second portion providing hole preponderant multiplication. This segmentation allows independent optimization of electron and hole multiplication processes, enabling high gain while maintaining fast response time for hyperfrequency applications.
Solution Approach 2:
Different regions of the multiplication zone are assigned different multiplication characteristics - the first portion is optimized for electron impact ionization while the second portion is optimized for hole impact ionization. This local differentiation of quality enables simultaneous achievement of high gain and high bandwidth by allowing each region to specialize in multiplying the carrier type that travels through it fastest.
2Reliability
If selective multiplication of only one carrier type is implemented, then strong gain is achieved without negative influence on bandwidth, but bandwidth remains too low for hyperfrequency applications above 10-20 GHz
Solution Approach 1:
The multiplication zone is divided into two distinct portions: a first portion for electron preponderant multiplication and a second portion for hole preponderant multiplication. This segmentation enables both carrier types to contribute to gain while maintaining the speed necessary for hyperfrequency operation, overcoming the bandwidth limitation of single-type multiplication structures.
Solution Approach 2:
The invention merges electron multiplication and hole multiplication in the same multiplication zone, with each type occurring in a different portion. This combination allows the benefits of both electron speed and hole multiplication to be utilized simultaneously, achieving hyperfrequency bandwidth with strong gain that neither selective multiplication alone could provide.
3Reliability
If the multiplication zone is optimized for high gain, then signal amplification is improved, but response time increases and bandwidth is reduced
Solution Approach 1:
By segmenting the multiplication zone into electron-preponderant and hole-preponderant portions, the invention allows high gain to be achieved through combined multiplication of both carrier types while maintaining fast response time. Each portion optimizes multiplication for its designated carrier type without the time penalty that would result from requiring both types to traverse the entire multiplication distance.
Solution Approach 2:
The invention adds a spatial dimension to the multiplication process by creating distinct regions for electron and hole multiplication within the multiplication zone. This dimensional organization allows simultaneous optimization of gain (through extended multiplication distance) and response time (through localized specialized multiplication regions).
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
This configuration significantly increases the bandwidth, allowing for hyperfrequency applications up to 20 GHz or more, with minimal noise and maintained gain, by prioritizing electron contribution and optimizing the electric field for efficient charge separation and evacuation.
Implementation Method 1
a second semiconducting zone called the multiplication zone, in contact with the second face of the first semiconducting zone and with a lower concentration of majority carriers than the first semiconducting zone, the second semiconducting zone being conformed to supply a multiplication of carriers by impact ionisation that is preponderant for electrons
Implementation Method 2
the fifth semiconducting zone being of the second type of conductivity and having a higher concentration of majority carriers than the second semiconducting zone so as to create an electric field in the third semiconducting zone
Implementation Method 3
at least one of the first and second semiconducting zones being formed from a semiconducting material with a suitable band gap width to promote absorption of the electromagnetic radiation
Data Source
AI summary
A structure of the avalanche photodiode type includes a first P doped semiconducting zone, a second multiplication semiconducting zone adapted to supply a multiplication that is preponderant for electrons, a fourth P doped semiconducting “collection” zone. One of the first and second semiconducting zones forms the absorption zone. The structure also includes a third semiconducting zone formed between the second semiconducting zone and the fourth semiconducting zone. The third semiconducting zone has an electric field in operation capable of supplying an acceleration of electrons between the second semiconducting zone and the fourth semiconducting zone without multiplication of carriers by impact ionisation.