AlGaN/GaN-HEMT Normally-off Gate Control via Polarization
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
AlGaN/GaN-HEMTs face challenges in achieving normally-off operation due to high concentration of two-dimensional electron gas, leading to difficulties in controlling sheet resistance, on-resistance, and leakage current, especially during the manufacturing process.
Innovation Solution
Incorporating a gate control layer with piezo and spontaneous polarization properties between the electron supply layer and the gate electrode, and forming a current path between the gate pad and gate electrode connection layers to control the threshold voltage and ensure a positive gate voltage offset, thereby enabling a complete normally-off operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If AlGaN/GaN-HEMT structure is used to achieve high-voltage resistance and high output, then high concentration of two-dimensional electron gas is obtained, but normally-off operation becomes difficult to realize
Solution Approach 1:
The patent divides the gate structure into multiple components: gate electrode, gate insulation layer, and gate control layer. The gate control layer is further segmented into first and second regions with different aluminum compositions, allowing independent control of threshold voltage and electron gas concentration to achieve normally-off operation while maintaining high output.
Solution Approach 2:
The gate control layer has non-uniform aluminum composition with a first region having lower aluminum content and a second region having higher aluminum content. This local quality variation creates different electrical properties in different areas, enabling the gate to simultaneously control threshold voltage for normally-off operation and maintain high electron gas concentration for high output.
2Ease of manufacture
If heat treatment is applied during manufacturing process, then manufacturing is facilitated, but sheet resistance increases and leakage current occurs due to damage to transit region
Solution Approach 1:
The gate control layer with optimized aluminum composition and thickness is designed beforehand to withstand heat treatment without causing excessive leakage current. The structural design provides a buffer against thermal damage, allowing heat treatment to be applied for manufacturing facilitation while maintaining reliability.
3Manufacturing precision
If gate control layer with piezo and spontaneous polarization is added, then threshold voltage control is improved, but device structure becomes more complex
Solution Approach 1:
The gate control layer acts as an intermediary between the gate electrode and the channel, utilizing piezo and spontaneous polarization effects to control threshold voltage. This intermediate layer provides precise voltage control without requiring complex external circuitry, balancing manufacturing precision with acceptable structural complexity.
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 solution allows for a reliable normally-off operation of AlGaN/GaN-HEMTs without increasing sheet resistance, on-resistance, or leakage current, with a simple structure that effectively controls the gate voltage threshold.
Implementation Method 1
a semiconductor layer that is formed above the compound semiconductor layer and is spontaneously polarized
Implementation Method 2
a semiconductor layer that is formed above the compound semiconductor layer and is spontaneously polarized
Data Source
AI summary
An AlGaN/GaN-HEMT has a structure including: compound semiconductor layers formed on a substrate; a gate electrode, a gate pad that has a current path formed between the gate electrode and itself, and a semiconductor layer that is spontaneously polarized and piezoelectrically polarized, which are formed on the compound semiconductor layer; and a gate electrode connection layer formed on the semiconductor layer, wherein the gate electrode connection layer and the gate electrode are electrically connected with each other. This structure which is relatively simple allows the AlGaN/GaN-HEMT to realize an intended normally-off operation without causing such inconveniences as increase in a sheet resistance, increase in an on-resistance, and increase in a leakage current.