GaN Buffer Layer Doping for Current Collapse
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Solution Overview
Problem
GaN-based High Electron Mobility Transistors (HEMTs) face current collapse issues due to electrons trapped by charge traps formed by impurities, which hinder the formation of a two-dimensional electron gas and lead to current collapse, despite reduced impurity doping helping to suppress this effect, accurate adjustment of the buffer layer thickness is necessary but not sufficient.
Innovation Solution
A semiconductor structure with a substrate and buffer layers co-doped with a transition metal and impurity, where the transition metal doping concentration remains constant and the impurity doping concentration is modulated periodically, with the transition metal concentration in the second buffer layer decreasing away from the substrate to avoid deep level traps and current collapse, and the impurity acting as an acceptor to compensate background electrons.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a transition metal is doped into the buffer layer below the 2DEG, then the pinch-off characteristic is improved, but electrons are trapped by charge traps formed by the impurity, leading to current collapse
Solution Approach 1:
The patent applies local quality by creating two distinct buffer layers with different doping characteristics. The first buffer layer near the substrate contains transition metal doping to improve pinch-off, while the second buffer layer closer to the 2DEG has reduced or no transition metal doping to prevent current collapse. This spatial differentiation of doping quality resolves the contradiction between improving pinch-off and preventing current collapse.
Solution Approach 2:
The buffer layer is segmented into two separate layers with different doping concentrations and compositions. The first buffer layer handles the pinch-off requirement, while the second buffer layer protects against current collapse. This segmentation allows each layer to independently fulfill its specific function without interfering with the other.
2Object-generated harmful factors
If the doping concentration of the impurity is reduced to suppress current collapse, then current collapse is suppressed, but the pinch-off characteristic deteriorates
Solution Approach 1:
The patent implements local quality by assigning different doping concentrations to different buffer layers. The first buffer layer has higher impurity doping to maintain pinch-off characteristics, while the second buffer layer has reduced impurity doping to suppress current collapse. This localized differentiation resolves the contradiction between maintaining pinch-off and suppressing current collapse.
3Object-generated harmful factors
If the thickness of the buffer layer is adjusted to suppress current collapse, then current collapse is reduced, but manufacturing precision requirements increase
Solution Approach 1:
The patent applies parameter changes by modifying the doping concentration parameter rather than relying solely on buffer layer thickness. By adjusting the doping concentration in the two buffer layers, the patent achieves current collapse suppression with more relaxed thickness control requirements, thereby reducing manufacturing precision demands.
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 dislocations, prevents current collapse, and balances dynamic characteristics by forming deep level traps to capture background electrons and reducing electron diffusion, while periodic impurity doping compensates for background electrons, thereby enhancing the pinch-off characteristic and reducing leakage current.
Implementation Method 1
By doping the transition metal in the first buffer layer of the semiconductor structure, the deep level trap may be formed to capture the background electrons
Implementation Method 2
the impurity may be as an acceptor impurity to compensate the background electrons, and then a concentration of the background electrons is reduced
Implementation Method 3
By using the periodic doping method, dislocations caused by doping, in the buffer layer may be effectively reduced
Data Source
AI summary
Embodiments of the present application provide a semiconductor structure and a manufacturing method therefor. A buffer layer is disposed on a substrate layer, and the buffer layer includes a first buffer layer and a second buffer layer. By doping a transition metal in the first buffer layer, a deep level trap may be formed to capture background electrons, and diffusion of free electrons toward the substrate may also be avoided. By decreasing a doping concentration of the transition metal in the second buffer layer, a tailing effect is avoided and current collapse is prevented. By doping periodically the impurity in the buffer layer, the impurity may be as an acceptor impurity to compensate the background electrons, and then a concentration of the background electrons is reduced. By using the periodic doping method, dislocations, caused by doping, in the buffer layer may be effectively reduced.