AlGaN/GaN HEMT Gate Electrode Trench Structure for Electric Field Relaxation
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Solution Overview
Problem
High electric fields concentrate on the fine gate end and over gate end of AlGaN/GaN HEMTs, leading to deterioration or breakdown of semiconductor crystals and protective insulating layers, significantly decreasing device reliability.
Innovation Solution
A compound semiconductor device with a protective insulating film featuring a first trench and a second trench, where the electrode fills the first trench and extends into the second trench, thinning the insulating film at the bottom of the second trench to reduce electric field concentration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If a gate electrode in overhanging shape is used to reduce gate capacitance and gate resistance, then high-frequency characteristics are improved, but high electric field concentration damages semiconductor crystals and protective insulating layers, decreasing device reliability
Solution Approach 1:
The protective insulating film is selectively thinned only in the second trench region located at the over gate end, while maintaining full thickness in other regions. This localized modification reduces electric field concentration specifically at the over gate end without compromising the protective function elsewhere, thereby resolving the contradiction between high-frequency performance and device reliability
2Reliability
If the protective insulating film is thinned to reduce electric field concentration, then device reliability is improved, but the protective function of the insulating film is compromised
Solution Approach 1:
The protective insulating film thickness is modified locally only in the second trench region where electric field concentration occurs, while maintaining the original protective thickness in all other regions. This selective thinning approach reduces electric field concentration to improve reliability without compromising the overall protective function of the insulating film
Solution Approach 2:
The second trench acts as an intermediary structure that introduces a controlled thin region of the protective insulating film. This intermediary modification allows electric field lines to be redistributed, reducing peak field concentration at the over gate end while the majority of the insulating film remains intact to provide protection
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 effectively relaxes electric field concentration around the gate electrode, enhancing device reliability and preventing breakdown, thereby achieving high withstand voltage and output power.
Implementation Method 1
High electric fields concentrate on the fine gate end and the over gate end. This high electric field damages semiconductor crystals at the fine gate end and damages a protective insulating that covers the semiconductor surface at the over gate end.
Implementation Method 2
Owing to piezoelectric polarization caused by the distortion and to spontaneous polarization of AlGaN, a high-concentration two-dimensional electron gas (2 DEG) is obtained.
Data Source
AI summary
A compound semiconductor device includes: a compound semiconductor layer; a protective insulating film that covers a top of the compound semiconductor layer; and a gate electrode formed on the protective insulating film, wherein the protective insulating film has a first trench and a second trench which is formed side by side with the first trench and in which the protective insulating film remains with only a predetermined thickness on the compound semiconductor layer, and wherein the gate electrode fills the first trench, and one end of the gate electrode is away from the first trench and located at least in the second trench.