GaN HEMT Gate Trench Reduces Leakage Current
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Solution Overview
Problem
Conventional GaN HEMT semiconductor devices face challenges with high gate leak current and current collapse, leading to increased on resistance and reduced drain current, making them unsuitable for high-power applications.
Innovation Solution
A semiconductor device with a MIS-type HEMT structure featuring a carrier traveling layer and a carrier supplying layer, where an insulating film with an inverted trapezoidal trench is formed between the source and drain electrodes, and a gate electrode is positioned from the bottom of the trench to the drain electrode, reducing electric field concentration and enhancing withstanding characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a schottky electrode is used for the gate structure of GaN HEMT, then withstanding characteristic is enhanced, but gate leak current increases
Solution Approach 1:
The gate structure is segmented into multiple functional layers: a MIS-type gate structure (metal-insulator-semiconductor) is implemented where the gate electrode is separated from the semiconductor layer by an insulating film. This segmentation allows the gate to maintain electrical isolation (reducing gate leak current) while still controlling the channel, resolving the contradiction between withstanding characteristic and gate leak current.
Solution Approach 2:
An insulating film is introduced as an intermediary layer between the gate electrode and the semiconductor layer. This intermediary prevents direct contact between the gate and channel, eliminating the gate leak current issue while maintaining gate control functionality, thus resolving the contradiction between withstanding characteristic and gate leak current.
2Speed
If conventional GaN HEMT structure is used, then high electron mobility is achieved, but current collapse increases and on resistance increases
Solution Approach 1:
The channel region is segmented into a two-layer structure consisting of a first semiconductor layer (higher bandgap) and a second semiconductor layer (lower bandgap). This segmentation creates distinct functional zones: the first layer provides high electron mobility through 2DEG formation at the heterointerface, while the second layer provides robust current conduction with lower on-resistance and reduced current collapse.
Solution Approach 2:
Different regions of the channel are assigned different material compositions and properties. The first semiconductor layer has higher aluminum content (higher bandgap) optimized for electron mobility, while the second layer has lower aluminum content (lower bandgap) optimized for current conduction. This local quality differentiation resolves the contradiction between electron mobility and current collapse.
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 gate leak current and current collapse, achieving lower on resistance and improved withstanding characteristics, enabling high-temperature operation and large driving currents in semiconductor devices.
Implementation Method 1
The GaN semiconductor element having the HEMT structure (hereinafter referred to simply as a GaN HEMT) can utilize two-dimensional electron gas that is generated around a hetero junction interface as carriers, so that it is capable of reducing on resistance.
Implementation Method 2
FETs (Field Effect Transistor) using a MIS (Metal Insulator Semiconductor) structure for a gate structure of a transistor using the GaN/AlGaN semiconductor material are being developed lately for the purpose of reducing a gate leak current
Implementation Method 3
the GaN HEMT uses a schottky electrode for its gate structure, so that it is capable of enhancing its withstanding characteristic
Data Source
AI summary
There is provided a semiconductor device and a method for fabricating the same whose withstanding characteristic may be enhanced and whose ON resistance may be reduced. A MIS-type HEMT includes a carrier traveling layer made of a group-III nitride semiconductor and formed on a supporting substrate, a carrier supplying layer made of a group-III nitride semiconductor and formed on the carrier traveling layer, source and drain electrodes formed on the carrier supplying layer, insulating films formed on the carrier supplying layer and a gate electrode formed on the insulating films. The insulating film is formed in a region interposed between the source and drain electrodes and has a trench whose cross-section is inverted trapezoidal and whose upper opening is wider than a bottom thereof. The gate electrode is formed at least from the bottom of the trench onto the insulating films on the side of the drain electrode.