GaN Ridge Gate Structure for Lower Leak Normally-Off HEMTs
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Solution Overview
Problem
Nitride semiconductor HEMTs with a normally-off type operation face issues with gate leak current, which affects the necessary gate voltage, power consumption, and heat generation, especially in high-frequency switching applications.
Innovation Solution
A nitride semiconductor device with a nitride semiconductor gate layer having a ridge portion in the [110] direction of the semiconductor crystal structure, surrounded by a source electrode and coupled by a ridge coupling portion, and an insulating film between the gate and nitride semiconductor gate layer, reduces gate leak current.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a p type GaN gate layer of ridge shape is used to eliminate the channel and achieve normally-off operation, then the device can be applied to power devices, but a gate leak current flows from the gate electrode to the source electrode via the p type GaN layer
Solution Approach 1:
The gate structure is segmented into multiple components: a gate insulating film layer, a nitride semiconductor gate layer with ridge portions, and a gate electrode. The ridge portions are separated by intervals and positioned at specific crystal orientations, creating discrete conduction path blocks that reduce overall gate leak current while maintaining normally-off operation capability
Solution Approach 2:
The nitride semiconductor gate layer is designed with non-uniform properties: ridge portions with specific crystal orientations ([110] direction) are positioned at intervals, while other regions have different characteristics. This local variation in crystal orientation and structure creates regions of low gate leak current density that reduce overall gate leak current
2Device complexity
If the gate leak current is large, then the device structure is simpler, but the gate voltage necessary for obtaining desired on resistance cannot be secured and power consumption increases
Solution Approach 1:
The invention changes key parameters of the gate structure: the nitride semiconductor gate layer is oriented with its length direction in the <110> crystal direction, ridge portions are positioned at specific intervals, and the gate insulating film has controlled thickness (5nm-50nm). These parameter changes reduce gate leak current density, enabling lower power consumption and better gate voltage control
3Device complexity
If the gate leak current is large, then the device structure is simpler, but heat generation increases in power circuit and control circuit portions
Solution Approach 1:
The nitride semiconductor gate layer employs local quality variation through ridge portions with specific crystal orientations (<110> direction) positioned at intervals. These locally optimized regions reduce gate leak current density, thereby reducing heat generation in the gate structure and surrounding circuit portions while maintaining overall structural simplicity
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 configuration effectively minimizes gate leak current, ensuring stable operation and reduced heat generation in high-frequency switching applications.
Implementation Method 1
a length direction of the ridge portion is a <110> direction of a semiconductor crystal structure that constitutes the second nitride semiconductor layer
Data Source
AI summary
A nitride semiconductor device 1 includes a first nitride semiconductor layer 13 that constitutes an electron transit layer, a second nitride semiconductor layer 14 that is formed on the first nitride semiconductor layer and constitutes an electron supply layer, a nitride semiconductor gate layer 15 that is disposed on the second nitride semiconductor layer, has a ridge portion 15A at least at a portion thereof, and contains an acceptor type impurity, a gate electrode 4 that is disposed at least on the ridge portion of the nitride semiconductor gate layer, a source electrode 3 that is disposed on the second nitride semiconductor layer and has a source principal electrode portion 3A parallel to the ridge portion, and a drain electrode 5 that is disposed on the second nitride semiconductor layer and has a drain principal electrode portion 5A parallel to the ridge portion. A length direction of the ridge portion is a [110] direction of a semiconductor crystal structure that constitutes the second nitride semiconductor layer.