GaN ESD Protection Device With Isolation Region
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Solution Overview
Problem
High voltage GaN devices face limitations in withstanding Electrostatic Discharge (ESD) events due to avalanche breakdown, particularly in scalability and material defects, leading to irreversible snapback and failure in ultra-high voltage applications.
Innovation Solution
A GaN ESD protection device with ohmic or Schottky contacts and a 2D electron gas region, featuring an isolation region between the contacts, a GaN channel region, and an AlGaN cap layer, which includes a buffer region and a ballast region to control breakdown and triggering voltage by varying the length of the isolation region, and optionally a substrate pump to adjust the substrate potential.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If GaN devices are used in ultra high voltage applications, then high electron mobility and voltage handling capability are improved, but avalanche breakdown occurs leading to irreversible snapback and device failure
Solution Approach 1:
The device is segmented into distinct functional regions: a first terminal region, a second terminal region, and a middle region containing the isolation structure. This segmentation prevents avalanche breakdown by creating isolated zones that control carrier multiplication and prevent the conditions necessary for snapback failure.
Solution Approach 2:
An isolation structure is introduced as an intermediary element between the source and drain terminals. This isolation structure, which may include isolation regions or isolation layers, acts as a mediator that controls the electric field distribution and prevents direct avalanche breakdown between the terminals, thereby enabling reversible snapback behavior.
2Quantity of substance
If device width is increased to achieve higher failure currents, then current handling capability is improved, but scalability is limited due to material defects and dislocations
Solution Approach 1:
The device structure is divided into multiple isolated regions that can be independently optimized. This segmentation allows the device to scale in width and area without proportionally increasing the impact of material defects, as each isolated region functions semi-independently and defects in one region do not necessarily propagate to others.
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 solution enables GaN devices to withstand ESD pulses without avalanche breakdown, providing reversible snapback capabilities and improved scalability for ultra-high voltage applications, such as grid level voltage devices, by distributing current density uniformly and managing high electric fields and heat generation.
Implementation Method 1
Due to the bandgap mismatch between the AlGaN and GaN material, the junction between the GaN channel region 108 and AlGaN cap 110 forms a conductive channel region known as a 2D electron gas (2DEG) channel
Implementation Method 2
the junction between the GaN channel region 108 and AlGaN cap 110 forms a conductive channel region known as a 2D electron gas (2DEG) channel
Implementation Method 3
The hole charge lowers the barrier at the channel-buffer interface, causing electrons to be injected from the source, thereby creating an avalanche region in the buffer
Implementation Method 4
This causes more holes to be generated and in turn causes more electrons to be injected from the source, leading to avalanche breakdown in the buffer layer
Implementation Method 5
The GaN channel region between the first terminal and said at least one isolation region may be longer than the length of the said isolation region, e.g., between 1 and 10 um, to define a ballast region for providing greater uniformity of the current density
Data Source
AI summary
In an ultra high voltage lateral GaN structure having a 2DEG region extending between two terminals, an isolation region is provided between the two terminals to provide for reversible snapback.