GaN HEMT Channel Carbon Segmentation for Current Collapse
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Solution Overview
Problem
Heterostructure field effect transistors suffer from current collapse and leak currents due to high carbon concentrations in channel layers, which affect device performance.
Innovation Solution
A semiconductor device with a GaN channel layer and AlxGa1-xN barrier layers is manufactured, where the carbon concentration of the uppermost channel layer is lower than the average concentration of the lower layers, achieved by varying the V/III ratio during growth to reduce carbon incorporation in the upper channel layer while maintaining high carbon concentration in the lower layers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If carbon is incorporated into the channel layer at a high concentration, then a leak current is suppressed, but a current collapse becomes conspicuous
Solution Approach 1:
The channel region is divided into multiple channel layers with different carbon concentrations. The lower channel layers have high carbon concentration to suppress leak current, while the upper channel layer has low carbon concentration to prevent current collapse. This segmentation allows each layer to perform its specific function independently.
Solution Approach 2:
Different regions of the channel layer are assigned different carbon concentrations based on their functional requirements. The lower channel layers are designed with high carbon concentration for leak current suppression, while the upper channel layer is designed with low carbon concentration for current collapse prevention. This local quality differentiation optimizes overall device performance.
2Reliability
If the carbon concentration is reduced in the upper channel layer, then current collapse is suppressed, but leak current increases
Solution Approach 1:
The channel region is segmented into multiple layers with differentiated carbon concentrations. The upper channel layer has low carbon concentration to prevent current collapse, while the lower channel layers have high carbon concentration to suppress leak current. This segmentation resolves the contradiction by distributing different functional requirements to different layers.
Solution Approach 2:
Multiple channel layers with different carbon concentrations are combined in a stacked configuration to achieve both leak current suppression and current collapse prevention simultaneously. The combined structure leverages the advantages of both high and low carbon concentration regions.
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 suppresses current collapse and leak currents by reducing carbon concentration in the upper channel layer and maintaining high carbon levels in the lower layers, enhancing device stability and performance.
Implementation Method 1
each of the plurality of semiconductor layers includes a channel layer made with GaN and a barrier layer provided in contact with an upper surface of the channel layer and made with AlxGa1-xN
Implementation Method 2
a third step of supplying the Ga source gas and the N source gas with a V/III ratio made higher than that in the first step and growing an upper channel layer made with GaN on the lower barrier layer
Data Source
AI summary
A semiconductor device according to the present invention includes a substrate, a plurality of semiconductor layers to be overlaid on the substrate and a gate electrode, a drain electrode, and a source electrode provided on the plurality of semiconductor layers, wherein each of the plurality of semiconductor layers includes a channel layer made with GaN and a barrier layer provided in contact with an upper surface of the channel layer and made with AlxGa1-xN, and a carbon concentration of the channel layer included in an uppermost semiconductor layer among the plurality of semiconductor layers is lower than an average value of carbon concentration of the channel layer included in the at least one semiconductor layer other than the uppermost semiconductor layer among the plurality of semiconductor layers.