Nitride Vertical FET Structure to Block Parasitic Diode Conduction
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Solution Overview
Problem
Conventional vertical FETs experience a decrease in breakdown voltage due to reverse conductive operations, where a great current flows from the source to the drain, leading to parasitic diode conduction.
Innovation Solution
A nitride semiconductor device is designed with a high-resistance layer between the nitride semiconductor layer and the p-type nitride semiconductor layer, along with a potential fixing electrode in Schottky contact, to block the current path of the parasitic p-n diode and prevent reverse conductive operations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If a conventional vertical FET is used for power converter circuit, then the device can operate as a power transistor, but a great current flows from source to drain when OFF, causing breakdown voltage to decrease
Solution Approach 1:
The device is segmented into multiple functional layers: a first nitride semiconductor layer for current conduction, a first high-resistance layer to block reverse current, and a first p-type nitride semiconductor layer for potential control. This segmentation allows the device to function as a power transistor while preventing reverse conductive operations that would otherwise degrade breakdown voltage.
Solution Approach 2:
A first high-resistance layer is introduced as an intermediary between the first nitride semiconductor layer and the first p-type nitride semiconductor layer. This intermediary layer has resistance higher than both adjacent layers, effectively blocking the parasitic p-n diode current path during reverse conductive operations while maintaining the power transistor's operational capabilities.
2Reliability
If a first high-resistance layer is added to block parasitic diode current, then breakdown voltage is maintained, but device structure becomes more complex
Solution Approach 1:
The first p-type nitride semiconductor layer serves multiple functions: it forms a p-n junction with the first nitride semiconductor layer to block reverse current, provides a potential fixing electrode contact point to maintain electrical integrity, and works with the high-resistance layer to suppress parasitic diode conduction. This multi-functionality reduces the need for additional separate components.
Solution Approach 2:
The device employs a composite structure combining n-type nitride semiconductor material, high-resistance nitride semiconductor material, and p-type nitride semiconductor material in specific configurations. This composite approach allows different regions to have optimized properties for their specific functions while maintaining overall device integration.
3Reliability
If a potential fixing electrode in Schottky contact is used, then current flow through parasitic p-n diode is prevented, but manufacturing process becomes more difficult
Solution Approach 1:
The potential fixing electrode is designed to form a Schottky contact with the first p-type nitride semiconductor layer by controlling the contact parameters - specifically using a metal material with appropriate work function that creates a Schottky barrier with the p-type nitride layer. This parameter control enables the electrode to fix potential and block current while using standard semiconductor fabrication processes.
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 proposed solution effectively suppresses the decrease in breakdown voltage during reverse conductive operations by preventing current flow through the parasitic p-n diode, thereby maintaining the device's electrical integrity.
Implementation Method 1
a first high-resistance layer above the first nitride semiconductor layer, the first high-resistance layer having a resistance higher than a resistance of the first nitride semiconductor layer
Implementation Method 2
The potential fixing electrode includes a material in Schottky contact with the first p-type nitride semiconductor layer
Data Source
AI summary
A nitride semiconductor device includes: a substrate; a nitride semiconductor layer above the substrate; a high-resistance layer above the nitride semiconductor layer; a p-type nitride semiconductor layer above the high-resistance layer; a first opening penetrating through the p-type nitride semiconductor layer and the high-resistance layer to the nitride semiconductor layer; an electron transport layer and an electron supply layer covering an upper portion of the p-type nitride semiconductor layer and the first opening; a gate electrode above the electron supply layer; a source electrode in contact with the electron supply layer; a second opening penetrating through the electron supply layer and the electron transport layer to the p-type nitride semiconductor layer; a potential fixing electrode in contact with the p-type nitride semiconductor layer at a bottom part of the second opening; and a drain electrode.