GaN HEMT Threshold Control via AlN Etch Stop Layer
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Solution Overview
Problem
The existing methods for forming normally-off GaN high electron mobility transistors (HEMTs) face challenges such as etching damage to the underlying AlGaN layer and complex, costly re-growth processes, which affect productivity and cost.
Innovation Solution
A GaN HEMT structure and fabrication method involving a substrate, buffer layer, GaN layer, AlGaN layers, AlN layers, and a p-type GaN layer, with a gate recess and passivation layer, allowing for direct contact and controlled thickness and aluminum content of the AlGaN layers to optimize electrical properties without etching damage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If directly etching the P-type GaN layer is used to form a normally-off GaN HEMT, then the fabrication process is simple, but etching damage occurs to the underlying AlGaN layer
Solution Approach 1:
An AlN layer is introduced as an intermediary between the P-type GaN layer and the AlGaN layer. This AlN layer serves as an etch stop layer that prevents etching damage to the underlying AlGaN layer during P-type GaN layer processing, while still allowing the fabrication process to proceed relatively simply.
Solution Approach 2:
The AlN layer is formed in advance before any etching operations on the P-type GaN layer. This preliminary action ensures that the protective barrier is already in place to prevent etching damage during subsequent fabrication steps.
2Manufacturing precision
If a re-growth method is used to grow an AlGaN layer on a P-type GaN layer, then etching damage is avoided, but the process becomes too complex with low productivity and high cost
Solution Approach 1:
Instead of using a complex re-growth process, a simpler AlN layer is deposited as an intermediary protective layer. This approach avoids etching damage without requiring complex re-growth equipment or multi-step processes, thereby reducing overall process complexity.
Solution Approach 2:
The invention changes the material parameter by using AlN instead of requiring AlGaN re-growth. This parameter change allows for simpler deposition processes while achieving the same protective function, thus reducing complexity and improving productivity.
3Ease of manufacture
If conventional fabrication methods are used, then the process is relatively simple, but productivity is low and cost is high due to process complexity
Solution Approach 1:
The AlN layer is formed as a preliminary protective barrier before any critical etching steps. This preliminary action prevents the need for complex protective measures during etching, streamlining the overall process and improving productivity by reducing the number of required process steps.
Data Source
AI summary
The present disclosure provides a high electron mobility transistor (HEMT) including a substrate; a buffer layer over the substrate; a GaN layer over the buffer layer; a first AlGaN layer over the GaN layer; a first AlN layer over the first AlGaN layer; a p-type GaN layer over the first AlN layer; and a second AlN layer on the p-type GaN layer.