P-Type Schottky GaN Gate Structure for TDDB Reliability
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Solution Overview
Problem
The reliability of Group III nitride-based transistor devices is limited by the time-dependent dielectric breakdown (TDDB) of the p-type Schottky gate junction, which occurs due to electrons from the two-dimensional electron gas being accelerated to high energies and causing defects and junction breakdown.
Innovation Solution
The introduction of one or more p-doped AlxGa(1−x)N layers within the p-doped Group III nitride structure of the p-type Schottky gate prevents injected electrons from reaching the Schottky depletion region, encouraging them to recombine in the lower p-doped GaN layer instead.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a p-type Schottky gate is used in Group III nitride-based transistor devices, then the device can achieve enhancement mode operation and normally off state, but the gate reliability is limited by time-dependent dielectric breakdown (TDDB) of the p-type Schottky gate junction
Solution Approach 1:
A p-doped AlxGa1-xN layer is introduced as an intermediary layer between the metal gate and the p-doped GaN layer. This intermediary layer prevents direct interaction between injected electrons and the Schottky depletion region, thereby reducing TDDB while maintaining enhancement mode operation. The layer acts as a buffer that modifies the electron transport path without compromising the gate's functional mode.
Solution Approach 2:
The gate structure is transformed from a simple p-doped GaN layer into a composite structure consisting of multiple layers: metal gate, p-doped AlxGa1-xN layer, and p-doped GaN layer. This composite structure combines the benefits of different materials to achieve both enhancement mode operation and improved reliability by distributing stress and modifying electron behavior across multiple interfaces.
2Productivity
If electrons are injected from the two-dimensional electron gas into the p-doped Group III nitride layer, then current conduction is enabled, but the injected electrons can be accelerated to very high energies in the Schottky depletion region leading to defect creation and junction breakdown
Solution Approach 1:
The p-doped AlxGa1-xN layer serves as a mediator that intercepts injected electrons before they can be accelerated to high energies in the Schottky depletion region. This intermediary layer provides a lower energy pathway for electron transport, enabling current conduction while preventing the harmful high-energy acceleration that causes defects and breakdown.
Solution Approach 2:
The invention converts the potentially harmful electron injection process into a beneficial current conduction mechanism by introducing the p-doped AlxGa1-xN layer. This layer guides the injected electrons through a controlled path that enables necessary current flow while preventing the harmful high-energy effects, effectively transforming a harmful process into a controlled beneficial one.
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 gate reliability by preventing electron acceleration and subsequent defect creation, thereby reducing the risk of junction breakdown and improving the overall performance of the transistor device.
Implementation Method 1
encouraging them to recombine in the lower p-doped GaN layer instead
Data Source
AI summary
In an embodiment, a Group III nitride-based transistor device is provided that includes a Group III nitride-based body and a p-type Schottky gate including a metal gate on a p-doped Group III nitride structure. The p-doped Group III nitride structure includes an upper p-doped GaN layer in contact with the metal gate and having a thickness d1, a lower p-doped Group III nitride layer having a thickness d2 and including p-doped GaN that is arranged on and in contact with the Group III nitride-based body, and at least one p-doped AlxGa1−xN layer arranged between the upper p-doped GaN layer and the lower p-doped Group III nitride layer, wherein 0<x<1. The thickness d2 of the lower p-doped Group III nitride layer is larger than the thickness d1 of the upper p-doped GaN layer.