Avalanche Photodetector Interface Layer Inhibits Breakdown
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing solid-state photodetector/imaging devices using amorphous selenium face limitations due to incipient breakdown at high electric fields, which prevents the simultaneous avalanche multiplication of both hole and electron charge carriers, limiting their sensitivity and reliability.
Innovation Solution
A photodetector/imaging device with a semi-insulating polymer interface layer between the photoconductive material and the readout layer, which restricts uncontrolled current flow and inhibits incipient breakdown, allowing for high electric fields that enable avalanche multiplication of both holes and electrons.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If high electric fields are applied to achieve avalanche multiplication of both holes and electrons, then sensitivity and avalanche gain are improved, but incipient breakdown occurs causing uncontrolled current rises and structural transformation
Solution Approach 1:
A charge injection layer is introduced as an intermediary component between the photoconductive layer and the electrode. This layer serves as a mediator that supplies charge carriers to the photoconductive material, enabling the system to achieve high avalanche gain without requiring excessively high electric fields that would cause incipient breakdown. The charge injection layer thus protects the photoconductive material from harmful high-field effects while maintaining the desired sensitivity enhancement.
2Reliability
If high electric fields are applied to enable avalanche multiplication, then avalanche gain increases to 10,000, but uncontrolled current flow occurs during electrical discharges
Solution Approach 1:
The charge injection layer implements a feedback mechanism by continuously supplying charge carriers to the photoconductive layer based on the operational needs. This feedback system ensures that sufficient carriers are available for avalanche multiplication to achieve high gain, while simultaneously preventing uncontrolled current flow by regulating the charge carrier supply, thus maintaining stable operation even at high avalanche gains of 10,000.
3Measurement precision
If high electric fields are applied to achieve simultaneous avalanche multiplication of holes and electrons, then sensitivity is enhanced, but the photoconductive material crystallizes due to heating
Solution Approach 1:
The charge injection layer acts as a thermal buffer and intermediary that enables sensitivity enhancement without direct high-field exposure of the photoconductive material. By injecting charges at lower fields, the system achieves the same detection sensitivity improvement without generating excessive heat that would cause crystallization of the amorphous photoconductive material, thus maintaining measurement precision while controlling temperature.
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 device achieves stable operation at high electric fields, significantly increasing avalanche gain to 10,000, preventing structural transformation of the photoconductive material and enabling both linear and Geiger region operations without adverse effects, thus enhancing sensitivity and reliability.
Implementation Method 1
Photoconductors are materials that are sensitive to visible light and other types of electromagnetic radiation (i.e. x-rays, ultraviolet radiation, infrared radiation etc.). When photons strike a photoconductor, they produce, through the process of ionization, two types of electric charge known as electrons and holes.
Implementation Method 2
At much higher electric fields (e.g. 80 V/μm and larger for a-Se), multiplication of charge carriers occurs. This property of multiplication of charge carriers, known as avalanche multiplication, is an important feature of certain ACPs such as a-Se
Implementation Method 3
at least one interface layer between the layer of photoconductive material and the readout layer, the interface layer coupling electrical charge to or from the layer of photoconductive material and being configured to inhibit uncontrolled rises in current in the photoconductive material during avalanche multiplication
Implementation Method 4
the high electric current at incipient breakdown heats up the ACP to the point where the photoconductive material of the ACP crystallizes
Data Source
AI summary
A photodetector/imaging device comprises a layer of photoconductive material converting incident electromagnetic radiation into electrical charges, the layer of photoconductive material being capable of avalanche multiplication when an electric field of sufficient magnitude is applied thereacross; a readout layer detecting the electrical charge; and at least one interface layer between the layer of photoconductive material and the readout layer, the interface layer coupling electrical charge to or from the layer of photoconductive material and being configured to inhibit uncontrolled rises in current in the photoconductive material during avalanche multiplication.