HEMT Gate-Drain Region Graded AlGaN Layer for Breakdown Voltage
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Solution Overview
Problem
Conventional High Electron Mobility Transistors (HEMTs) face limitations in breakdown voltage due to electric field concentration on the gate, which is not effectively addressed by existing methods such as field plates, p-doping, or ion implantation, leading to unreliable operation and a small process window.
Innovation Solution
The method involves forming a first and second material layer on a substrate with different lattice constants, where the second material layer between the gate and drain is modified by implanting doping materials or changing its thickness through etching or plasma treatment to reduce the two-dimensional electron gas (2DEG) density, thereby reducing stress and increasing breakdown voltage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the distance between gate and drain is extended to increase breakdown voltage, then the electric field concentration on gate is reduced, but the device area increases and manufacturing complexity increases
Solution Approach 1:
The patent applies local quality by creating a graded AlGaN layer with varying aluminum composition (x value) in specific regions. The second AlGaN layer has a different aluminum composition (x2) than the first AlGaN layer (x1), where x2 < x1. This local compositional variation modifies the electric field distribution specifically in the region between gate and drain without changing the overall device geometry, thereby increasing breakdown voltage without increasing device area.
2Reliability
If field plate is used to disperse electric field, then the electric field concentration on gate is reduced, but the device area increases and the field plate size cannot be continuously increased to improve the effect
Solution Approach 1:
The patent changes the material composition parameter (aluminum content x) in the AlGaN layer to modify electric field distribution. By creating a graded structure where the aluminum composition varies from x1 to x2 across the second AlGaN layer, the patent achieves electric field dispersion through material parameter modification rather than geometric expansion. This approach improves electric field distribution without requiring additional device area.
3Reliability
If p-doping or ion implantation is used to reduce electric field concentration, then the breakdown voltage increases, but the process window is small and control is difficult
Solution Approach 1:
The patent extracts the need for complex doping processes by using a purely structural approach with graded AlGaN layers. Instead of introducing dopants through ion implantation or in-situ doping, the invention achieves electric field control through compositional grading of the AlGaN material itself. This eliminates the small process window and control difficulties associated with doping while achieving similar or superior electric field management.
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 approach effectively disperses the electric field, increases breakdown voltage, and improves the reliability of HEMTs by reducing the concentration of the electric field on the gate, while maintaining sufficient on-current and process margin.
Implementation Method 1
modulation doping is applied to the HEMT using a polarization field generated by spontaneous polarization and piezo polarization
Implementation Method 2
modulation doping is applied to the HEMT using a polarization field generated by spontaneous polarization and piezo polarization
Implementation Method 3
implanting different materials (e.g., doping materials) in an exposed region of the second material layer
Implementation Method 4
annealing the implanted region
Implementation Method 5
changing a thickness of the second material layer between the gate and the drain
Data Source
AI summary
A method of manufacturing a High Electron Mobility Transistor (HEMT) may include forming first and second material layers having different lattice constants on a substrate, forming a source, a drain, and a gate on the second material layer, and changing the second material layer between the gate and the drain into a different material layer, or changing a thickness of the second material layer, or forming a p-type semiconductor layer on the second material layer. The change in the second material layer may occur in an entire region of the second material layer between the gate and the drain, or only in a partial region of the second material layer adjacent to the gate. The p-type semiconductor layer may be formed on an entire top surface of the second material layer between the gate and the drain, or only on a partial region of the top surface adjacent to the gate.