Dual Thickness Barrier Layer HEMT for Normally-Off Operation
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Solution Overview
Problem
High-electron-mobility Field Effect Transistors (HEMTs) face challenges in achieving a normally-off state due to their heterojunction configuration, which leads to self-conducting transistors, and there is a need to improve performance parameters like leakage current, threshold voltage, and voltage blocking capability.
Innovation Solution
A semiconductor device with a heterojunction semiconductor body featuring a barrier layer with thicker and thinner sections, where the gate structure is positioned on the thinner section to control the two-dimensional charge carrier gas, allowing for independent adjustment of threshold voltage and drain-source on-state resistance without increasing leakage current.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a heterojunction configuration is used to achieve high electron mobility, then conduction performance is improved, but the transistor becomes self-conducting and cannot achieve normally-off state
Solution Approach 1:
The barrier layer is designed with different thicknesses in different regions: a first thickness under the gate structure and a second thickness in the drift region. This local variation allows the gate to effectively control the channel formation while maintaining high electron mobility in the drift region, enabling normally-off operation without sacrificing conduction performance.
2Ease of operation
If measures are taken to prevent self-conduction to achieve normally-off state, then control capability is improved, but leakage current increases
Solution Approach 1:
The thickness of the barrier layer is changed as a key parameter: a thinner first thickness under the gate enables effective depletion and normally-off operation, while a thicker second thickness in the drift region maintains low resistance. This parameter optimization allows the transistor to achieve normally-off state with minimal leakage current.
3Ease of operation
If the barrier layer thickness is increased to reduce leakage current, then threshold voltage control is improved, but drain-source on-state resistance increases
Solution Approach 1:
The barrier layer exhibits different thicknesses in different locations: a thinner region under the gate for effective threshold voltage control and normally-off operation, and a thicker region in the drift area for maintaining low on-state resistance. This spatial differentiation resolves the contradiction between leakage control and conduction performance.
4Ease of manufacture
If a uniform barrier layer is used to simplify manufacturing, then device complexity is reduced, but independent adjustment of threshold voltage and on-state resistance is not possible
Solution Approach 1:
The barrier layer is designed with locally different thicknesses, creating distinct functional zones that enable independent optimization of threshold voltage and on-state resistance. This can be achieved through selective epitaxial growth or etching processes, maintaining manufacturing feasibility while gaining parameter independence.
Solution Approach 2:
The barrier layer is segmented into different thickness regions, with the first section under the gate and the second section in the drift region. This segmentation allows each region to be independently optimized for its specific function while being manufactured as an integrated structure.
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 enables a normally-off HEMT with improved threshold voltage and ruggedized gate structure capable of withstanding high switching voltages, while maintaining low drain-source on-state resistance, thus enhancing the overall performance of the transistor.
Implementation Method 1
The second type III-V semiconductor layer has a different bandgap as the first type III-V semiconductor layer such that a first two-dimensional charge carrier gas forms at an interface between the first and second type III-V semiconductor layers
Implementation Method 2
a gate structure is formed on the thinner section of the second type III-V semiconductor layer, the gate structure being configured to control a conductive connection between the first and second input-output electrodes
Implementation Method 3
The heterojunction semiconductor body is provided such that the second type III-V semiconductor layer has a thicker section and a thinner section... allowing for independent adjustment of threshold voltage and drain-source on-state resistance
Data Source
AI summary
A semiconductor device includes a heterojunction semiconductor body including a first and second type III-V semiconductor layers with different bandgaps such that a first two-dimensional charge carrier gas forms at an interface between the two layers. The second type III-V semiconductor layer includes a thicker section and a thinner section. A first input-output electrode is on the thicker section and is in ohmic contact with the first two-dimensional charge carrier gas. A second input-output electrode is formed on the thinner section and is in ohmic contact with the first two-dimensional charge carrier gas. A gate structure is formed on the thinner section and is configured to control a conductive connection between the first and second input-output electrodes. The gate structure is laterally spaced apart from a transition between the thicker and thinner sections of the second type III-V semiconductor layer.