GaN HEMT Buffer Layer Carbon Gradient for Stable 2DEG
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Solution Overview
Problem
Current GaN-based HEMT designs face issues with electron discharge due to lower potential wells in undoped GaN buffer layers, leading to increased resistance and reduced two-dimensional electron gas (2DEG) formation.
Innovation Solution
A buffer layer with a bottom portion having a higher carbon concentration than a top portion is used, creating a step-profile carbon concentration gradient to inhibit electron injection into the lower potential well, thereby preventing discharge and enhancing 2DEG formation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional buffer layer with uniform carbon concentration is used, then the fabrication process is simple, but electron injection into the buffer layer occurs leading to increased resistance and unstable 2DEG
Solution Approach 1:
The buffer layer is divided into multiple portions (first portion, second portion, third portion) with different carbon concentrations. The first portion has higher carbon concentration to inhibit electron injection, while the second and third portions have progressively lower concentrations to maintain 2DEG stability. This local differentiation of material properties resolves the contradiction by preventing electron injection without requiring complex external structures.
Solution Approach 2:
The carbon concentration parameter is varied across different portions of the buffer layer. By changing the carbon concentration from the first portion (higher) to the second and third portions (lower), the patent creates a gradient that prevents electron injection while maintaining stable 2DEG formation, thus improving reliability without adding structural complexity.
2Reliability
If the buffer layer lacks a potential well structure, then the fabrication is simpler, but electron injection increases resistance and affects device performance
Solution Approach 1:
Instead of using a complex potential well structure, the patent applies local quality by creating different carbon concentration zones within the buffer layer. The first portion with higher carbon concentration acts as a barrier to electron injection, while subsequent portions with lower concentrations maintain the desired electrical properties, achieving resistance control through material composition rather than structural complexity.
Solution Approach 2:
The patent changes the carbon concentration parameter across the buffer layer portions to achieve the desired electrical characteristics. By progressively reducing carbon concentration from the first to the third portion, the patent creates a gradient that controls electron injection and maintains stable 2DEG, improving resistance control while keeping the fabrication process relatively simple.
3Object-affected harmful factors
If carbon concentration is increased in the buffer layer, then electron injection is inhibited, but the formation of 2DEG may be affected
Solution Approach 1:
The patent applies local quality by concentrating the high carbon concentration only in the first portion of the buffer layer, while the second and third portions have progressively lower concentrations. This localized approach inhibits electron injection at the critical interface without preventing 2DEG formation in the channel region, resolving the contradiction between blocking electron injection and maintaining 2DEG reliability.
Solution Approach 2:
The patent uses parameter changes by creating a carbon concentration gradient that transitions from high in the first portion to lower in the second and third portions. This gradual parameter change allows the buffer layer to simultaneously inhibit electron injection (through the high carbon concentration portion) and maintain stable 2DEG formation (through the lower carbon concentration portions).
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 electron discharge and increases the conductivity of the device by maintaining carriers in the channel region, improving the overall performance of the HEMT.
Implementation Method 1
forming a buffer layer on a substrate... the buffer layer further includes a bottom portion having a first carbon concentration and a top portion having a second carbon concentration... inhibiting electron injection into the lower level and preventing discharge effects, thereby maintaining a stable 2DEG
Data Source
AI summary
A method for fabricating a high electron mobility transistor (HEMT) includes the steps of forming a buffer layer on a substrate, forming a barrier layer on the buffer layer, forming a p-type semiconductor layer on the barrier layer, forming a gate electrode on the p-type semiconductor layer, and then forming a source electrode and a drain electrode adjacent to two sides of the gate electrode. Preferably, the buffer layer further includes a bottom portion having a first carbon concentration and a top portion having a second carbon concentration, in which the second carbon concentration is less than the first carbon concentration and a thickness of the bottom portion is less than a thickness of the top portion.