GaN FET Isolating Gate Structure for Leakage Current
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Solution Overview
Problem
Gallium nitride (GaN) FETs are susceptible to leakage current through the two-dimensional electron gas outside the channel area, which is not effectively addressed by existing technologies.
Innovation Solution
The implementation of an isolating gate structure outside the channel area, formed concurrently with the gate of the GaN FET, which electrically isolates regions of the two-dimensional electron gas, reducing or eliminating leakage current.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If GaN FET is used for power switches, then high bandgap and high thermal conductivity are achieved, but leakage current from drain to source through two-dimensional electron gas occurs
Solution Approach 1:
The gate structure is segmented into a main gate portion over the channel and an isolating gate portion extending beyond the channel boundaries. This segmentation allows the isolating gate to specifically target and block leakage current paths in the two-dimensional electron gas that extend outside the channel area, while the main gate maintains normal FET operation.
Solution Approach 2:
The isolating gate portion acts as an intermediary structure between the main gate and the leakage current paths. By extending the gate electrode beyond the channel boundaries into the region where two-dimensional electron gas exists, it creates an intermediate control mechanism that can deplete carrier density in these external regions and block leakage current without interfering with the primary switching function.
2Object-generated harmful factors
If gate structure is extended beyond channel area to block leakage current, then leakage current is reduced, but device complexity increases
Solution Approach 1:
The isolating gate portion is merged with the main gate structure, forming a single continuous gate electrode. Both portions are formed from the same gate material and share common gate contacts and control mechanisms. This merging approach allows leakage current blocking functionality to be added without requiring separate gate structures, control circuits, or additional fabrication steps for a second gate system.
Solution Approach 2:
The extended gate structure serves multiple functions: the main gate portion controls the primary current flow through the channel for switching operation, while the isolating gate portion simultaneously blocks leakage current paths in the two-dimensional electron gas. This multi-functionality is achieved within a single gate structure, avoiding the need for separate specialized components.
3Ease of manufacture
If isolating gate structure is formed concurrently with gate, then manufacturing process is simplified, but manufacturing precision requirements increase
Solution Approach 1:
The gate structure, including both the main gate portion and the isolating gate portion, is formed as a single patterned layer during the preliminary stages of device fabrication, before subsequent processing steps. By establishing the complete gate geometry early in the manufacturing process, the relative positions and dimensions of both gate portions are simultaneously defined, ensuring their proper spatial relationship without requiring additional alignment steps between separately formed structures.
Data Source
AI summary
A semiconductor device containing a GaN FET has an isolating gate structure outside the channel area which is operable to block current in the two-dimensional electron gas between two regions of the semiconductor device. The isolating gate structure is formed concurrently with the gate of the GaN FET, and has a same structure as the gate.