Nitride Semiconductor Device Gate-Drain Distance
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Solution Overview
Problem
Conventional high electron mobility transistors (HEMTs) with a GaN/AlGaN heterojunction structure are typically normally-on type, leading to safety concerns during abnormalities, and they exhibit high resistance to voltage and decreased high-frequency characteristics due to a short distance between the gate and drain electrodes, limiting their suitability for high-frequency and power devices.
Innovation Solution
A nitride semiconductor device with a heterojunction structure comprising a channel layer, a barrier layer, and a gate layer, where the gate layer has a smaller band gap than the channel layer, allowing for a two-dimensional electron gas formation and enabling a normally-off operation with increased distance between the gate and drain electrodes, thus enhancing high-frequency characteristics and switching speed.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the gate length is increased to increase the distance between gate and drain electrodes, then the resistance to voltage is improved, but the high-frequency characteristics and switching speed deteriorate
Solution Approach 1:
The patent introduces a third nitride semiconductor layer with a smaller band gap than the channel layer, positioned between the channel layer and the drain electrode. This vertical layering approach increases the gate-drain distance in the vertical dimension without requiring an increase in the horizontal gate length, thereby maintaining high-frequency characteristics while improving voltage resistance.
Solution Approach 2:
The third nitride semiconductor layer is specifically positioned in the region between the channel layer and the drain electrode, where it provides localized electrical isolation. This layer has different band gap properties than the channel layer, creating a specific electrical characteristic in the critical gate-drain region without affecting the overall gate structure or channel performance.
2Reliability
If the gate length is increased to increase the distance between gate and drain electrodes, then the resistance to voltage is improved, but the high-frequency characteristics deteriorate
Solution Approach 1:
The patent introduces a third nitride semiconductor layer with a smaller band gap than the channel layer, positioned between the channel layer and the drain electrode. This vertical layering approach increases the gate-drain distance in the vertical dimension without requiring an increase in the horizontal gate length, thereby maintaining high-frequency characteristics while improving voltage resistance.
3Ease of manufacture
If a conventional GaN/AlGaN heterojunction structure is used, then the device can be fabricated, but the gate threshold voltage is negative resulting in normally-on type operation
Solution Approach 1:
The patent changes the band gap parameter of the semiconductor layers by introducing a third nitride semiconductor layer with a smaller band gap than the channel layer. This parameter change modifies the polarization effects and carrier distribution, enabling positive gate threshold voltage and normally-off type operation while maintaining fabricability through standard heterojunction growth techniques.
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 structure achieves high resistance to voltage, improved high-frequency performance, and increased switching speed by increasing the gate-drain distance without increasing gate length, making it suitable for high-frequency and power devices.
Implementation Method 1
a high-density carrier layer called a two-dimensional carrier gas is formed by a polarization effect
Data Source
AI summary
A nitride semiconductor device includes: a main semiconductor region comprising a first nitride semiconductor layer having a first band gap, and a second nitride semiconductor layer having a second band gap larger than the first band gap, a heterojunction being formed between the first nitride semiconductor layer and a the second nitride semiconductor layer such that two-dimensional electron gas layer can be caused inside the first nitride semiconductor layer based on the heterojunction; a source electrode formed on the main semiconductor region; a drain electrode formed on the main semiconductor region and separated from the source electrode; a third nitride semiconductor layer formed on the first nitride semiconductor layer and between the source electrode and the drain electrode; and a gate electrode formed on the third nitride semiconductor layer. The third nitride semiconductor layer has a third band gap smaller than the first band gap.