GaN HEMT with Segmented AlGaN Layer for High Mobility and Voltage
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Solution Overview
Problem
Conventional field effect transistors using group III nitride semiconductors have not achieved both high mobility and high withstand voltage simultaneously, limiting their suitability for power devices.
Innovation Solution
A field effect transistor design featuring a GaN electron transit layer with an AlxGa1-xN electron supplying layer, a recess region, and a specific step structure under the drain electrode, along with a gate insulating film and electrode, which generates a high-density two-dimensional electron gas for high mobility and withstand voltage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If conventional GaN MOSFET structures are used, then high withstand voltage can be achieved, but mobility remains insufficient
Solution Approach 1:
The patent applies local quality by creating different Al composition ratios in different regions of the electron supplying layer. The region under the gate electrode has a first Al composition ratio optimized for high electron density and mobility, while the region under the drain electrode has a second Al composition ratio optimized for withstanding high electric fields. This spatial variation in material composition allows each region to be optimized for its specific functional requirements, simultaneously achieving high mobility and high withstand voltage.
2Strength
If high Al composition ratio is used in electron supplying layer, then withstand voltage improves, but electron density and mobility decrease
Solution Approach 1:
The patent implements local quality by spatially varying the Al composition ratio within the electron supplying layer. The first region (under gate) uses a lower Al composition ratio to maintain high electron density, while the second region (under drain) uses a higher Al composition ratio to enhance withstand voltage. This localized optimization resolves the contradiction by allowing different compositions in different functional zones rather than using a uniform composition throughout.
Solution Approach 2:
The electron supplying layer is segmented into multiple regions with different Al composition ratios. This segmentation allows the layer to perform multiple functions simultaneously: the first region provides high electron density for mobility, while the second region provides high breakdown voltage capability. By dividing the layer into functionally distinct segments, the patent overcomes the limitation of single-composition designs.
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 design achieves high mobility exceeding 1000 cm2/Vs and high withstand voltage, enabling normally-off operation with a 2-zone RESURF region, effectively addressing the limitations of previous devices.
Implementation Method 1
an electron supplying layer formed on the electron transit layer and formed of AlxGa1-xN (0.01≦x≦0.4), said electron supplying layer having a band gap energy different from that of the electron transit layer
Implementation Method 2
a high-density two-dimensional electron gas for high mobility and withstand voltage
Data Source
AI summary
A field effect transistor formed of a semiconductor of a III group nitride compound, includes an electron running layer formed on a substrate and formed of GaN; an electron supplying layer formed on the electron running layer and formed of AlxGa1-xN (0.01≦x≦0.4), the electron supplying layer having a band gap energy different from that of the electron running layer and being separated with a recess region having a depth reaching the electron running layer; a source electrode and a drain electrode formed on the electron supplying layer with the recess region in between; a gate insulating film layer formed on the electron supplying layer for covering a surface of the electron running layer in the recess region; and a gate electrode formed on the gate insulating film layer in the recess region. The electron supplying layer has a layer thickness between 5.5 nm and 40 nm.