GaN Superjunction Vertical Transistor for High Breakdown Voltage
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Solution Overview
Problem
GaN-based vertical structure power transistors face limitations in achieving high breakdown voltage and high output current due to surface states and trade-offs between breakdown voltage and on-resistance, with conventional lateral structures experiencing voltage collapse and performance sacrifices.
Innovation Solution
A GaN-based superjunction vertical power transistor is developed, featuring a superjunction composite structure with an N−-GaN layer, a P-GaN current blocking layer, and a thin barrier Al(In, Ga)N/GaN heterostructure, which expands the superjunction space charge region and enhances the breakdown voltage, while avoiding etching issues through epitaxial growth and passivation layers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional GaN-based vertical structure power transistor uses a P-GaN Current Blocking Layer and a single N-type lightly doped layer as the voltage withstanding layer, then the device can be manufactured with existing processes, but the breakdown voltage is limited and on-resistance cannot be optimized simultaneously
Solution Approach 1:
The voltage withstanding layer is segmented into multiple alternating P-type and N-type superjunction columns, creating a composite structure that distributes the electric field. This segmentation allows the breakdown voltage to be enhanced without proportionally increasing the on-resistance, as the depleted regions in P and N columns work together to block voltage while maintaining conductive paths
Solution Approach 2:
The patent employs a composite superjunction structure combining P-type GaN and N-type GaN layers with alternating doping profiles. This composite material approach creates a voltage withstanding layer that achieves higher breakdown voltage than single-material structures, while the thin barrier Al(In, Ga)N/GaN heterostructure adds another layer of material complexity to optimize both voltage blocking and current conduction
2Ease of manufacture
If GaN-based lateral structure power transistors are used to achieve large size and low cost, then manufacturing cost is reduced, but high output current cannot be obtained and high voltage current collapse occurs due to surface states
Solution Approach 1:
The patent inverts the conventional lateral structure approach by adopting a vertical structure configuration. Instead of having current flow laterally across the surface where surface states cause collapse, the current flows vertically through the superjunction columns, bypassing the surface state problem while maintaining high output current capability
Solution Approach 2:
The superjunction columns provide localized high-quality voltage withstanding regions with optimized doping profiles, while the areas between columns maintain good conductivity. This local quality differentiation allows the device to achieve both high breakdown voltage and high output current without the surface state limitations of lateral structures
3Device complexity
If the voltage withstanding layer uses a single N-type lightly doped layer to simplify the structure, then manufacturing is easier, but the breakdown voltage is limited and trade-off with on-resistance occurs
Solution Approach 1:
The voltage withstanding layer is segmented into multiple alternating P-type and N-type superjunction columns, creating a composite structure that distributes the electric field. This segmentation allows the breakdown voltage to be enhanced without proportionally increasing the on-resistance, as the depleted regions in P and N columns work together to block voltage while maintaining conductive paths
Solution Approach 2:
The patent transitions from a single-layer voltage withstanding structure to a multi-layer superjunction composite structure, adding the dimension of vertical layering with alternating P and N types. This dimensional change enables the electric field to be managed in multiple zones, achieving higher breakdown voltage without the linear increase in on-resistance that would result from simply thickening a single layer
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 solution effectively increases breakdown voltage and enables high-power applications by mitigating peak breakdown electric fields and recovering two-dimensional electron gas, promoting an etch-free enhanced gate structure for GaN-based vertical power transistors.
Implementation Method 1
two-dimensional electron gas between the gate and the source in the thin barrier Al(In, Ga)N/GaN heterostructure is recovered by passivation of the passivation layer between the gate and the source
Implementation Method 2
two-dimensional electron gas between the gate and the source in the thin barrier Al(In, Ga)N/GaN heterostructure is recovered by passivation of the passivation layer between the gate and the source
Data Source
AI summary
A GaN-based superjunction vertical power transistor and a manufacturing method thereof. The transistor includes: a N−-GaN layer; a first P-GaN layer as a current blocking layer, formed on the N−-GaN layer and having a gate region window; and a thin barrier Al(In, Ga)N/GaN heterostructure conformally formed on the current blocking layer and filling the bottom and one or more sidewalls of the gate region window, wherein the N−-GaN layer has an etched groove completely or partially filled with a second P-type GaN layer, an N+-GaN layer is formed under the second P-type GaN layer, and the N+-GaN layer is in direct contact with the second P-type GaN layer and the N−-GaN layer to form a superjunction composite structure.