GaN HEMT Recess Structure for Normally-Off Operation
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
GaN-based HEMTs face challenges in achieving normally-off operation with high threshold voltage and reducing leak current, especially when high voltage is applied, due to their inherent material properties and manufacturing difficulties in vertical structures.
Innovation Solution
The introduction of a recess structure and specific layer configurations, including undoped i-AlN and Fe-doped GaN layers, along with a recess electrode forming a schottky junction, suppresses two-dimensional electron gas formation at the surface, enabling normally-off operation and increasing the threshold voltage beyond conventional limits.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a gate recess structure is used to enable normally-off operation, then the normally-off operation is achieved, but the threshold voltage becomes 1 V or less and leak current increases
Solution Approach 1:
The patent applies local quality by creating a specific doped region (n-type doped region) with different electrical properties than the surrounding undoped GaN layer. This localized doping creates a potential barrier that suppresses leak current while maintaining normally-off operation, resolving the contradiction between achieving normally-off operation and preventing leak current.
Solution Approach 2:
The patent changes the electrical parameters by introducing n-type doping in a specific region, which alters the carrier concentration and potential distribution. This parameter change increases the threshold voltage above 1 V while maintaining normally-off operation, thereby reducing leak current.
2Object-generated harmful factors
If the threshold voltage is increased by changing material, then the threshold voltage increases, but sufficient current cannot be obtained or the device becomes easy to break
Solution Approach 1:
Instead of changing the bulk material properties throughout the device, the patent applies local doping only in a specific region. This localized approach increases the threshold voltage without compromising the overall current capability or mechanical strength of the GaN-based device.
Solution Approach 2:
The n-type doped region acts as an intermediary structure that mediates between the gate electrode and the undoped GaN layer. It provides the necessary potential control to increase threshold voltage while maintaining sufficient current flow through the channel.
3Reliability
If a gate recess structure is used, then normally-off operation is enabled, but it is difficult to use for high voltage applications due to noise and unstable operations
Solution Approach 1:
By changing the electrical parameters through localized n-type doping, the patent increases the threshold voltage above 1 V, which provides better noise immunity and stabilizes operations under high voltage conditions while maintaining normally-off operation.
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 reduces leak current and increases the threshold voltage, ensuring stable operation under high voltage conditions and facilitating mass production, particularly in vertical structures.
Implementation Method 1
a recess electrode forming a schottky junction
Data Source
Figure 1
Figure 2
Figure 3~4
AI summary
An i-GaN layer (electron transit layer), an n-GaN layer (compound semiconductor layer) formed over the i-GaN layer (electron transit layer), and a source electrode, a drain electrode and a gate electrode formed over the n-GaN layer (compound semiconductor layer) are provided. A recess portion is formed inside an area between the source electrode and the drain electrode of the n-GaN layer (compound semiconductor layer) and at a portion separated from the gate electrode.