GaN HEMT Termination Layer for Leakage Reduction
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Solution Overview
Problem
High voltage GaN HEMTs face performance degradation due to surface reactions on the metallic Schottky layer, which is exposed to air during fabrication and operation, leading to reduced breakdown voltage and increased leakage current.
Innovation Solution
A high voltage GaN HEMT structure is developed with a termination layer, such as InGaN, Fe-doped GaN, or SiN, disposed on the Schottky layer to prevent surface reactions and enhance passivation, thereby reducing leakage current and increasing breakdown voltage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the Schottky layer is exposed to air during fabrication and operation, then surface reactions such as oxidation occur on the Schottky layer surface, but this degrades the performance of the HEMT and decreases the effectiveness of passivation
Solution Approach 1:
A termination layer is introduced as an intermediary between the Schottky layer and the external environment. This termination layer prevents direct exposure of the Schottky layer to air, thereby blocking oxidation reactions while maintaining the passivation effectiveness. The termination layer acts as a protective mediator that resolves the contradiction between maintaining Schottky layer integrity and preventing surface reactions.
Solution Approach 2:
The termination layer is deposited on the Schottky layer before the device is exposed to air during fabrication and operation. This preliminary protective action prevents surface oxidation from occurring in the first place, rather than attempting to remediate oxidation after it has degraded the Schottky layer performance.
2Reliability
If surface reactions occur on the Schottky layer, then leakage current increases and breakdown voltage decreases, but adding a termination layer increases device structure complexity
Solution Approach 1:
The termination layer modifies the surface properties of the Schottky layer by changing the material composition at the surface. This parameter change prevents surface reactions and thereby maintains high breakdown voltage and low leakage current, while the added layer serves multiple functions simultaneously.
Solution Approach 2:
The termination layer serves multiple functions: it prevents surface oxidation, maintains passivation effectiveness, and preserves the electrical characteristics of the Schottky layer. By consolidating these functions into a single layer, the design minimizes the increase in device complexity while achieving multiple protective effects.
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 termination layer effectively protects the Schottky layer from oxidation, improving the reproducibility and reliability of the HEMT by reducing surface traps and enhancing electron mobility, resulting in increased breakdown voltage and reduced leakage current.
Implementation Method 1
The GaN-based HEMT device is capable of maximizing electron mobility by forming a quantum well at the heterojunction interface between the AlGaN layer, which has a large band gap, and the GaN layer, which has a narrower band gap. As a result, electrons are trapped in the quantum well.
Implementation Method 2
By exposing the Schottky layer to air, surface reactions such as oxidation may occur on the surface of the Schottky layer. These surface reactions may degrade the performance of the HEMT... A termination layer, which is disposed on the second active layer, includes InGaN... effectively protects the Schottky layer from oxidation
Data Source
AI summary
A semiconductor device is provided that includes a substrate, a first active layer disposed over the substrate, and a second active layer disposed on the first active layer. The second active layer has a higher bandgap than the first active layer such that a two-dimensional electron gas layer arises between the first active layer and the second active layer. A termination layer, which is disposed on the second active layer, includes InGaN. Source, gate and drain contacts are disposed on the termination layer.