GaN HEMT Vertical Drain Structure for High Breakdown Voltage
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Solution Overview
Problem
GaN-based HEMTs face challenges in achieving high breakdown voltages due to dielectric breakdown issues when operating at high voltages, particularly due to the concentration of electric fields between the gate and drain electrodes, leading to short circuits and creeping discharges.
Innovation Solution
The field effect transistor design spatially separates the gate and drain electrodes on different planes, with the drain electrode positioned on the opposing side of the semiconductor structure, and incorporates a second semiconductor layer with a higher bandgap energy to enhance breakdown voltage and reduce carrier scattering, while an intermediate layer further mitigates electric field concentration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the gate and drain electrodes are disposed on the same plane in a laterally structured device, then the device structure is simplified and easier to manufacture, but the breakdown voltage between electrodes cannot be maintained above several hundred volts due to insulation difficulties and electric field concentration
Solution Approach 1:
The patent transitions from a lateral structure where all electrodes are on the same plane to a vertical structure where the drain electrode is positioned on the opposite surface of the semiconductor layer relative to the gate and source electrodes. This dimensional change increases the spacing between high-voltage electrodes, reducing electric field concentration and enabling breakdown voltages above several hundred volts while maintaining manufacturing feasibility through standard semiconductor processing techniques
2Power
If a higher voltage is applied between source and drain electrodes to achieve high power output, then the power output increases, but a portion of the device becomes subjected to large concentration of electric field resulting in device breakdown and short circuit
Solution Approach 1:
By positioning the drain electrode on the opposite surface of the semiconductor layer, the patent creates a vertical current path that distributes the electric field more uniformly throughout the device volume. This reduces peak electric field concentration at any single location, enabling the application of higher voltages for high power output without causing dielectric breakdown or short circuits
Solution Approach 2:
The semiconductor layer itself acts as an intermediary between the gate/source electrodes on one surface and the drain electrode on the opposite surface. This intermediate structure provides a controlled path for current flow and electric field distribution, preventing direct exposure of critical regions to excessive electric field concentrations that would cause breakdown
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
This configuration significantly increases the breakdown voltage between the drain-source and drain-gate electrodes, enabling higher power outputs and stable operation by reducing electric field concentration and preventing dielectric breakdown.
Implementation Method 1
the n-type AlGaN layer 74 serving as a carrier supply layer supplies electrons to the undoped GaN layer 73 serving as an electron transit layer, and thus such supplied electrons transit, with high mobility, through the region 73a which serves as a channel
Implementation Method 2
The illustrated GaN-based HEMT 700... disposed on or above the semiconductor structure are the gate electrode and the source electrode; and the drain electrode is disposed on opposing side of the semiconductor structure where the gate electrode is disposed... this arrangement enables a drain's breakdown voltage to be increased
Implementation Method 3
The illustrated GaN-based HEMT 700, in a sequential lamination from the bottom on an insulating sapphire substrate 71, contains an AlN buffer layer 72, an undoped GaN layer 73
Data Source
AI summary
A field effect transistor (FET) includes a first semiconductor layer and a second semiconductor layer, the second semiconductor layer being formed on the first semiconductor layer and having a band gap energy greater than that of the first semiconductor layer. The first and second semiconductor layers are made of a Group III-V compound semiconductor layer, formed on the first semiconductor layer are a gate electrode 36 and a source electrode 35, formed on the second semiconductor layer is a drain electrode 37, and the drain electrode and the gate electrode are formed respectively on opposing planes of a semiconductor structure which contains the first and second semiconductor layers. This arrangement enables a drain's breakdown voltage to be increased in the FET, because the gate electrode 36 and the drain electrode 37 are respectively disposed, in a spatial separation of each other, on different planes instead of the same plane of the semiconductor structure.