GaN Body Electrode Structure With Graded p-Type Layer Contact
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Solution Overview
Problem
In GaN and Ga2O3 based FETs, the formation of p-type regions is challenging, leading to high contact resistance and reduced avalanche breakdown voltage due to etching damage during dry etching, which increases on-resistance and reduces channel mobility.
Innovation Solution
A semiconductor device with a p-type layer structure comprising a first p-type layer and a second p-type layer, where the second p-type layer has a higher acceptor concentration than the first, reducing contact resistance while suppressing the increase in on-resistance, achieved by depositing these layers sequentially and ensuring the second p-type layer is exposed at the bottom surface of the recess.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the acceptor concentration of the body layer is increased to reduce contact resistance, then contact resistance decreases, but channel mobility is reduced and on-resistance increases
Solution Approach 1:
The patent applies local quality by creating a multi-layer p-type structure where different regions have different acceptor concentrations. The first p-type layer has a first acceptor concentration optimized for channel mobility, while the second p-type layer has a higher acceptor concentration optimized for contact resistance. This spatial differentiation of material properties allows simultaneous optimization of both contact resistance and on-resistance without compromising channel performance.
2Ease of manufacture
If dry etching is used to form a recess for body electrode contact, then body electrode can be formed, but etching damage reduces acceptor concentration and increases contact resistance
Solution Approach 1:
The patent applies preliminary action by forming the second p-type layer with high acceptor concentration before the dry etching process. This pre-positioned high-concentration layer compensates for the acceptor concentration reduction that will occur during subsequent etching damage. The layer is strategically placed at the bottom of the recess structure so that even after etching removes some material, sufficient acceptors remain to maintain low contact resistance.
3Device complexity
If a single p-type layer is used, then structure is simple, but cannot simultaneously achieve low contact resistance and low on-resistance
Solution Approach 1:
The patent applies segmentation by dividing the p-type layer into multiple distinct layers (first p-type layer and second p-type layer), each with different acceptor concentrations and thicknesses. The first layer has lower acceptor concentration for maintaining channel mobility, while the second layer has higher acceptor concentration for reducing contact resistance. This segmentation allows independent optimization of each layer's properties to fulfill different functional requirements within the same device structure.
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 effectively reduces contact resistance and maintains lower on-resistance, enhancing hole extraction and avalanche breakdown voltage while minimizing etching damage effects.
Implementation Method 1
the p-type layer has a first p-type layer, and a second p-type layer deposited on the first p-type layer and having an acceptor concentration higher than the acceptor concentration of the first p-type layer
Data Source
AI summary
The present invention provides a semiconductor device in which the contact resistance of the body electrode is reduced without reducing the channel mobility. The p-type layer is a Mg-doped p-GaN layer deposited on the first re-type layer. The p-type layer has a two-layer structure in which a first p-type layer and a second p-type layer are sequentially deposited. The second p-type layer has a Mg concentration higher than the Mg concentration of the first p-type layer. The recess is formed in a predetermined position on the surface of the second n-type layer, and has a depth passing through the second n-type layer and reaching the second p-type layer. The body electrode is formed on the bottom surface of the recess in contact with the p-type layer exposed thereon.