Ridge HEMT Structure for Higher On-Current and Stable Operation
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Solution Overview
Problem
High electron mobility transistors (HEMTs) fabricated from GaN-based materials face challenges in achieving high on-current while maintaining device stability due to the formation of damaged layers during the etching process for ridge formation, which affects the performance and cost of the device.
Innovation Solution
A method involving the formation of a buffer layer, patterned mask to create ridges and trenches, removal of the damaged layer, deposition of a barrier layer, and a p-type semiconductor layer, followed by the formation of source and drain electrodes, which increases the effective gate width and on-current without increasing the device area and cost.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If ridge-shaped structures are formed on the buffer layer to increase effective gate width, then on-current is improved, but damaged layers are formed on the ridges which worsen device stability
Solution Approach 1:
The damaged layer formed during ridge creation is not discarded but converted into a functional component. By selectively removing portions of the damaged layer and combining it with barrier and semiconductor layers, the patent creates a composite structure where the damaged layer serves as part of the active device region, thus converting the harmful defect into a beneficial feature that contributes to current conduction.
Solution Approach 2:
The patent creates a composite structure consisting of multiple layers including the damaged layer, barrier layer, and semiconductor layer. This composite approach allows each layer to contribute its specific properties: the damaged layer provides conduction pathways, the barrier layer offers protection and potential additional functionality, and the semiconductor layer provides the active device characteristics, together achieving both high on-current and device stability.
2Area of moving object
If the buffer layer is removed to form ridges, then effective gate width is increased, but damaged layers remain on the ridges affecting performance
Solution Approach 1:
Instead of uniformly treating the entire ridge structure, the patent applies selective removal processes that target specific portions of the damaged layer while preserving other portions. This local differentiation allows the ridge structure to have varying properties in different regions: some areas have removed damaged layers for optimal conduction, while other areas retain damaged layers that are subsequently converted into functional components.
Solution Approach 2:
The damaged layer is intentionally created as part of the ridge formation process itself, rather than being treated as an unwanted byproduct to be completely eliminated. This preliminary creation of the damaged layer structure allows for subsequent selective manipulation and conversion into functional elements, improving overall manufacturing efficiency and device performance.
3Ease of manufacture
If damaged layers are not removed, then manufacturing process is simplified, but device performance and stability deteriorate
Solution Approach 1:
The patent transforms the damaged layer from a harmful defect requiring complete removal into a beneficial functional component. By implementing selective removal followed by layer deposition, the process maintains relative simplicity while converting the previously harmful damaged layer into an active part of the device structure that contributes to current conduction and overall device functionality.
Data Source
AI summary
A high electron mobility transistor (HEMT) includes a buffer layer on a substrate, ridges extending along a first direction on the buffer layer, gaps extending along the first direction between the ridges, a p-type semiconductor layer extending along a second direction on the ridges and inserted into the gaps, and a source electrode and a drain electrode adjacent to two sides of the p-type semiconductor layer. Preferably, the source electrode and the drain electrode are extending along the second direction and directly on top of the ridges.