GaN HEMT Buffer Layer Doping Profile for Current Collapse Control
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Solution Overview
Problem
Existing GaN-type high electron mobility transistors (HEMTs) face challenges with current collapse and device leakage due to impurity-related charge traps and inaccurate control of buffer layer thickness.
Innovation Solution
A semiconductor structure with a buffer layer that includes carbon element doping, featuring a first portion with increasing carbon concentration and a second portion with decreasing carbon concentration, along with Al composition insertion layers, to enhance breakdown voltage and prevent current collapse.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If carbon impurities are doped to improve pinch-off characteristics or increase cut-off voltage, then breakdown voltage is improved, but current collapse occurs due to electrons captured by charge traps
Solution Approach 1:
The buffer layer is divided into a first portion with increasing carbon concentration and a second portion with decreasing carbon concentration. The first portion (adjacent to substrate) has higher carbon concentration to increase breakdown voltage, while the second portion (adjacent to channel layer) has lower carbon concentration to reduce charge traps and prevent current collapse. This spatial variation in carbon concentration resolves the contradiction between improving breakdown voltage and preventing current collapse.
Solution Approach 2:
The buffer layer is segmented into multiple portions with different carbon concentration profiles. By dividing the buffer layer into a first portion and a second portion with distinct carbon doping characteristics, the patent enables different functional zones within the same layer to simultaneously achieve high breakdown voltage and low current collapse.
2Reliability
If impurity doping concentration is reduced to suppress current collapse, then current collapse is suppressed, but breakdown voltage decreases
Solution Approach 1:
Instead of uniformly reducing carbon concentration throughout the buffer layer, the patent applies local quality by creating a spatial gradient where the second portion (near channel layer) has lower carbon concentration to suppress current collapse, while the first portion (near substrate) maintains higher carbon concentration to preserve breakdown voltage.
3Ease of manufacture
If buffer layer thickness is not accurately controlled, then manufacturing is simplified, but current collapse cannot be eliminated
Solution Approach 1:
The patent changes the parameter of carbon concentration distribution within the buffer layer from uniform to graded/varied. By controlling the carbon concentration to increase in the first portion and decrease in the second portion, the patent achieves reliable current collapse suppression through compositional control rather than relying solely on precise thickness control, thereby maintaining ease of manufacture while improving reliability.
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 proposed structure increases breakdown voltage without affecting dynamic characteristics, prevents current collapse, and reduces device leakage, thereby improving the performance and reliability of GaN-type HEMTs.
Implementation Method 1
the buffer layer includes carbon element doping
Implementation Method 2
The band gap of the first insertion layer is greater than the band gap of the first portion and the band gap of the second portion
Data Source
AI summary
Provided are a semiconductor structure and a preparation method thereof. The semiconductor structure includes a substrate, a buffer layer, a channel layer, and a barrier layer that are sequentially stacked. The buffer layer includes carbon element doping. The buffer layer includes a first portion and a second portion that are distributed in a stack. The first portion is disposed on a side of the buffer layer adjacent to the substrate. In the direction of the substrate pointing to the channel layer, the carbon concentration in the first portion gradually increases with a preset trend, and the carbon concentration in the second portion gradually decreases. The buffer layer also includes a first insertion layer disposed between the first portion and the second portion. The first insertion layer includes an Al composition.