Vertical Ga2O3 Power FET Structure for >1 kV Breakdown
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Solution Overview
Problem
Existing high power Ga2O3 transistors have not achieved breakdown voltages greater than 1 kV, limiting their high voltage and high current operation capabilities.
Innovation Solution
The development of high power vertical gallium oxide (Ga2O3) transistors with a substrate, an n-type Ga2O3 drift layer, a fin-shaped or nanowire-shaped semiconducting channel, and a conductive gate layer, allowing for both depletion and enhancement mode operations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If lateral Ga2O3 MOSFETs with field plates are used, then breakdown voltage reaches 750 V, but breakdown voltage cannot exceed 1 kV
Solution Approach 1:
The patent transitions from lateral channel configuration to vertical channel configuration, changing the dimensional orientation of current flow and electric field distribution. This vertical architecture enables breakdown voltages exceeding 1 kV by utilizing the vertical drift layer structure, which provides more efficient voltage blocking capability compared to lateral designs
Solution Approach 2:
The patent modifies key structural parameters including drift layer thickness (5-20 μm), doping concentration (10^15-10^17 atoms/cm³), and channel dimensions to optimize breakdown voltage. By adjusting these parameters in the vertical device structure, breakdown voltages greater than 1 kV are achieved while maintaining high current density
2Reliability
If Ga2O3 material is used, then wide bandgap enables high voltage operation, but fabrication process compatibility with existing GaN vertical transistor processes is poor
Solution Approach 1:
The patent optimizes Ga2O3 layer parameters including thickness (5-20 μm for drift layer), doping concentration (10^15-10^17 atoms/cm³), and crystal orientation to achieve both high voltage operation and compatibility with existing semiconductor fabrication processes. These parameter adjustments enable the material to exhibit both superior electrical properties and manufacturability
3Power
If vertical Ga2O3 device structure is implemented, then high current density (>1 kA/cm²) and high voltage (>1 kV) operations are enabled, but device complexity increases
Solution Approach 1:
The vertical device is segmented into distinct functional layers: drift layer, active layer, and contact layer, each with specific doping concentrations and thicknesses. This segmentation allows independent optimization of each layer for its specific function while maintaining overall device simplicity and manufacturability
Solution Approach 2:
The vertical Ga2O3 device structure serves multiple functions simultaneously: the drift layer provides voltage blocking, the active layer enables high current conduction, and the overall structure supports both high voltage and high current operations. This multi-functionality reduces the need for additional components, thereby managing complexity
Data Source
AI summary
A vertical gallium oxide (Ga2O3) device having a substrate, an n-type Ga2O3 drift layer on the substrate, an, n-type semiconducting channel extending from the n-type Ga2O3 drift layer, the channel being one of fin-shaped or nanowire shaped, an n-type source layer disposed on the channel; the source layer has a higher doping concentration than the channel, a first dielectric layer on the n-type Ga2O3 drift layer and on sidewalls of the n-type semiconducting channel, a conductive gate layer deposited on the first dielectric layer and insulated from the n-type source layer, n-type semiconducting channel as well as n-type Ga2O3 drift layer, a second dielectric layer deposited over the conductive gate layer, covering completely the conductive gate layer on channel sidewalls and an ohmic source contact deposited over the n-type source layer and over at least a part of the second dielectric layer; the source contact being configured not to be in electrical contact with the conductive gate layer.