HEMT Gate Electrode Material Selection for Pinch-Off Voltage
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Solution Overview
Problem
Enhancement-mode high electron mobility transistors face challenges in improving pinch-off voltage without increasing on-state resistance, particularly when using a p-type GaN gate electrode, which reduces carrier mobility and increases on-state resistance.
Innovation Solution
Incorporating a gate dielectric layer between the channel layer and the gate electrode, with a gate electrode material having a sum of electron affinity and bandgap energy of at least 6 eV, such as a polycrystalline p-type semiconductor material, to increase the threshold voltage and improve carrier mobility by maintaining a portion of the barrier layer under the gate structure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a p-type GaN gate electrode is used to improve pinch-off voltage, then the threshold voltage increases, but carrier mobility is reduced and on-state resistance increases
Solution Approach 1:
An AlN layer is introduced as an intermediary between the p-type GaN gate electrode and the AlGaN barrier layer. This AlN layer has a wider bandgap and higher electron affinity, which allows it to deplete electrons from the barrier layer more effectively, improving pinch-off characteristics without requiring the gate electrode to directly contact the barrier layer, thus preserving carrier mobility in the channel
Solution Approach 2:
The gate structure uses a composite configuration combining p-type GaN gate electrode material with an AlN insertion layer. This composite structure leverages the high threshold voltage properties of p-type GaN while the AlN layer prevents direct contact that would harm carrier mobility, achieving both high pinch-off voltage and maintained carrier mobility
2Reliability
If multi-finger configurations are used to ensure all fingers are turned off, then pinch-off voltage increases, but device complexity increases
Solution Approach 1:
The invention changes the material parameters of the gate electrode system by introducing AlN with specific electron affinity and bandgap properties. This parameter change enables effective electron depletion and high threshold voltage without requiring complex multi-finger configurations, simplifying the device structure while maintaining reliability
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 enhances the threshold voltage and reduces on-state resistance, achieving better pinch-off characteristics and maintaining carrier mobility, particularly useful in multiple finger transistor designs.
Implementation Method 1
the gate electrode includes a first gate electrode film that contacts the gate dielectric layer, wherein the first gate electrode film includes a material, wherein the material has a sum of an electron affinity and a bandgap energy of at least 6 eV
Data Source
AI summary
An electronic device can include a channel layer including AlzGa(1-z)N, where 0≤z≤0.1; a gate dielectric layer; and a gate electrode of a high electron mobility transistor (HEMT). The gate dielectric layer can be disposed between the channel layer and the gate electrode. The gate electrode includes a gate electrode film that contacts the gate dielectric layer, wherein the gate electrode film can include a material, wherein the material has a sum of an electron affinity and a bandgap energy of at least 6 eV. In some embodiments, the material can include a p-type semiconductor material. The particular material for the gate electrode film can be selected to achieve a desired threshold voltage for an enhancement-mode HEMT. In another embodiment, a portion of the barrier layer can be left intact under the gate structure. Such a configuration can improve carrier mobility and reduce Rdson.