GaN Heterojunction Structure with Deactivated Regions for TDDB Reliability
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Solution Overview
Problem
GaN transistors face dynamic RDS_ON stability issues due to charge trapping during high-voltage operations, and the implementation of hybrid drain structures degrades the time-dependent dielectric breakdown (TDDB) lifetime by exacerbating local electric fields.
Innovation Solution
A modified heterojunction structure with deactivated regions is introduced, where the structural configuration of the heterojunction is altered to reduce the 2DEG concentration, and foreign atoms are selectively implanted or the GaN-based alloy layer is thinned to weaken the 2DEG formation in specific areas, thereby mitigating electric field exacerbation and dielectric failures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If hybrid drain contact structures are implemented, then dynamic RDS_ON stability is improved, but TDDB lifetime is degraded due to exacerbated local electric fields
Solution Approach 1:
The patent introduces deactivated regions with modified heterojunction structure (thinned or removed GaN-based alloy layer) in specific areas between the gate and drain contact structures. This creates local variations in 2DEG concentration, forming low 2DEG concentration regions that reduce local electric field strength while maintaining high 2DEG concentration in the channel for conductivity. This local quality modification resolves the contradiction by allowing hybrid drain structures to improve dynamic RDS_ON stability without causing excessive electric field concentration that would degrade TDDB lifetime.
2Object-affected harmful factors
If deactivated regions with reduced 2DEG concentration are introduced, then electric field exacerbation is mitigated, but device complexity increases
Solution Approach 1:
The patent modifies the GaN-based alloy layer thickness parameter in specific regions to create deactivated regions. By controlling the thickness (thinning or removing the layer) during epitaxial growth, the 2DEG concentration is locally reduced without fundamentally changing the overall device architecture. This parameter-based approach reduces electric field exacerbation while avoiding the complexity of introducing entirely new structural elements or components.
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 modified structure reduces dynamic RDS_ON increase to 30% or less and mitigates TDDB lifetime degradation by reducing the electric field between the field plate and device channel, enhancing the reliability of GaN transistors.
Implementation Method 1
GaN-based semiconductor devices typically include a heterojunction structure that induces highly-mobile 2-dimensional electron gas (2DEG) at the interface of two dissimilar semiconductor materials
Implementation Method 2
a first layer of electrons with a first electron concentration at a surface of the GaN layer facing the GaN-based alloy layer
Implementation Method 3
foreign atoms are selectively implanted or the GaN-based alloy layer is thinned to weaken the 2DEG formation in specific areas
Data Source
AI summary
GaN devices with a modified heterojunction structure and methods of making thereof are described. The GaN device comprises a heterojunction structure modified to include one or more deactivated regions. The heterojunction structure of the deactivated regions has different structural configurations than that of the as-grown heterojunction structure. The locally confined structural alteration of the heterojunction structure weakens or prohibits 2DEG formation in the deactivated regions. Moreover, the amount of net charges mapped to a field plate positioned above the heterojunction structure can be locally reduced or eliminated. Consequently, the electric field present between the heterojunction structure and the field plate can be reduced.