Open Drain Junction Field Effect Transistor High Voltage Operation
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Solution Overview
Problem
Conventional junction field effect transistors (JFETs) face challenges in operating at high voltages without experiencing gate leakage current, low frequency noise, and maintaining stability, which are crucial for precision analog applications.
Innovation Solution
The development of n-channel and p-channel JFETs with an open drain configuration, where the drain is designed to allow higher voltage operation without increasing transistor size, by spreading equipotential electric field lines and reducing impact ionization rates, along with the use of silicide blocks and surface shields to reduce noise and enhance stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional JFET structure is used, then device size remains compact, but gate leakage current occurs at high voltages
Solution Approach 1:
The drain is opened in the vertical dimension by removing the p-type buried layer and deep n-type regions beneath it, allowing the drain region to extend downward. This dimensional change spreads the equipotential lines vertically, reducing the horizontal electric field strength at the gate-drain junction and thereby suppressing gate leakage current while enabling higher voltage operation
Solution Approach 2:
The electrical parameters of the drain region are fundamentally changed by removing the p-type buried layer and deep n-type regions, transforming the drain from a confined junction to an extended open structure. This parameter change in the drain's electrical configuration reduces the electric field concentration, allowing operation at higher voltages without gate leakage
2Power
If voltage is increased to improve performance, then drive current capability improves, but impact ionization increases causing noise and reliability issues
Solution Approach 1:
By opening the drain vertically and spreading equipotential lines in the vertical dimension, the horizontal electric field strength is reduced. This dimensional redistribution of electric field lines lowers the impact ionization rate in the channel region, reducing noise and harmful effects while maintaining high voltage operation and drive current capability
Solution Approach 2:
The electric field distribution parameters are changed by the open drain structure, which redistributes the voltage gradient. This parameter change in electric field distribution reduces peak field strengths that cause impact ionization, thereby reducing noise and reliability issues while maintaining power capability
3Ease of manufacture
If conventional JFET structure is used, then manufacturing is simple, but low frequency noise is high
Solution Approach 1:
The drain structure parameter is changed from a conventional confined junction to an open extended structure. This parameter change in the drain configuration reduces low frequency noise by minimizing impact ionization and associated carrier generation, while the overall manufacturing process remains relatively simple using standard semiconductor fabrication techniques
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 design enables JFETs to operate at significantly higher voltages before experiencing gate leakage, improves device stability, and reduces noise, making them suitable for high-voltage precision analog applications without increasing the transistor's dimensions.
Implementation Method 1
Opening the drain essentially spreads equipotential lines of respective electric fields developed at the drains of the devices so that the local electric fields, and hence the impact ionization rates are reduced
Implementation Method 2
the local electric fields, and hence the impact ionization rates are reduced
Data Source
AI summary
The disclosure herein pertains to fashioning an n channel junction field effect transistor (NJFET) and/or a p channel junction field effect transistor (PJFET) with an open drain, where the open drain allows the transistors to operate at higher voltages before experiencing gate leakage current. The open drain allows the voltage to be increased several fold without increasing the size of the transistors. Opening the drain essentially spreads equipotential lines of respective electric fields developed at the drains of the devices so that the local electric fields, and hence the impact ionization rates are reduced to redirect current below the surface of the transistors.