HEMT Passivation Layer for Normally-Off Defect Suppression
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Solution Overview
Problem
Current high electron mobility transistors (HEMTs) face challenges in achieving a normally-off characteristic and efficient operation due to the generation of dangling bonds and nitrogen vacancy defects during the formation of p-type semiconductor layers, which reduce hole concentration and efficiency.
Innovation Solution
Incorporating a passivation layer made of a quaternary material such as AlGaOxNy on the barrier layer to suppress the formation of dangling bonds and prevent gallium diffusion, thereby maintaining the hole concentration and improving the reliability and uniformity of the HEMT.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a p-type semiconductor layer is formed on the barrier layer to achieve normally-off characteristic, then the transistor can be turned off effectively, but dangling bonds and nitrogen vacancy defects are generated which reduce hole concentration and efficiency
Solution Approach 1:
A passivation layer is formed on the barrier layer before forming the p-type semiconductor layer. This preliminary passivation action prevents the generation of dangling bonds and nitrogen vacancy defects during subsequent processing, thereby maintaining high hole concentration while achieving normally-off characteristic.
Solution Approach 2:
The passivation layer acts as an intermediary between the barrier layer and the p-type semiconductor layer. It mediates the interaction by providing a protective interface that prevents defect generation while allowing the p-type layer to function properly for normally-off operation.
2Reliability
If conventional passivation methods are used, then some protection is provided, but gallium diffusion occurs and defects are not sufficiently suppressed
Solution Approach 1:
The passivation layer is formed from a quaternary material system (Al-Ga-O-N) rather than conventional binary or ternary materials. This composite material provides superior protection against gallium diffusion and defect suppression due to its optimized chemical composition and bonding characteristics.
Solution Approach 2:
The chemical composition parameters of the passivation layer are optimized by controlling the ratios of Al, Ga, O, and N elements. By adjusting these parameters, the passivation layer achieves maximum effectiveness in preventing gallium diffusion and suppressing defects while maintaining structural stability.
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 use of a quaternary passivation layer enhances the normally-off characteristic of HEMTs by reducing defects and gallium diffusion, leading to improved on-resistance stability and reduced dispersion, thus increasing the overall efficiency and reliability of the transistors.
Implementation Method 1
A HEMT includes semiconductor layers with different electrical polarization characteristics. In a HEMT, a semiconductor layer having a relatively large polarization may induce formation of a 2-dimensional electron gas (hereinafter, a 2DEG) in another semiconductor layer heterojunctioned therewith.
Implementation Method 2
Incorporating a passivation layer made of a quaternary material such as AlGaOxNy on the barrier layer to suppress the formation of dangling bonds and prevent gallium diffusion
Data Source
AI summary
The present disclosure provides a high electron mobility transistor including a channel layer; a barrier layer on the channel layer and configured to induce formation of a 2-dimensional electron gas (2DEG) to the channel layer; a p-type semiconductor layer on the barrier layer; a first passivation layer on the barrier layer and including a quaternary material of Al, Ga, O, and N; a gate electrode on the p-type semiconductor layer; and a source electrode and a drain electrode provided on both sides of the barrier layer and separated from the gate electrode.