Indium HEMT Layer Structure for Lattice Matching and Fast Switching
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Solution Overview
Problem
Existing high electron mobility transistor (HEMT) structures face challenges in achieving optimal lattice matching and reducing electron injection, which can lead to layer separation and increased production costs.
Innovation Solution
The HEMT structure incorporates a seed layer with multiple AlN layers, a graded layer with varying aluminum gallium nitride compositions, and a buffer layer doped with p-type dopants to reduce lattice mismatch and electron injection, while using indium-containing layers to enhance charge carrier concentration and switching speed.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a HEMT structure is formed with conventional layers, then the basic transistor function is achieved, but lattice mismatch occurs leading to layer separation and reduced reliability
Solution Approach 1:
The buffer layer is segmented into multiple sub-layers with progressively varying compositions (e.g., AlGaN layers with decreasing Al content from bottom to top). This gradual segmentation of the buffer structure allows progressive lattice matching, reducing dislocation density and preventing layer separation while maintaining structural integrity
Solution Approach 2:
The invention changes the compositional parameters of the buffer layer by incorporating multiple AlGaN layers with different aluminum contents. This parameter variation creates a graded structure that progressively adapts the lattice constant from the substrate to the active InGaN layer, reducing lattice mismatch and improving reliability
2Reliability
If electron injection is reduced to prevent layer separation, then layer stability improves, but charge carrier concentration decreases affecting switching speed
Solution Approach 1:
The invention applies local quality by creating regions with different properties: the buffer layer has graded composition to prevent electron injection and maintain stability, while the active InGaN layer has high indium content to provide high charge carrier concentration for fast switching. Each layer is optimized for its specific function
Solution Approach 2:
The graded AlGaN buffer layer acts as an intermediary between the substrate and the active InGaN layer. It mediates the lattice mismatch and electron injection issues while allowing the active layer to maintain high charge carrier concentration, thus enabling both stability and fast switching
3Speed
If indium-containing layers are added to increase charge carrier concentration, then switching speed improves, but manufacturing complexity and production costs increase
Solution Approach 1:
The invention merges the functions of lattice matching and charge carrier generation into a unified multi-layer buffer structure. The graded AlGaN layers simultaneously address lattice mismatch and control electron injection, while the final InGaN layer provides high carrier concentration, combining multiple functions into 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
This approach reduces lattice mismatch, minimizes dislocations, and increases the charge carrier concentration in the two-dimensional electron gas, resulting in improved switching speed and reliability of the HEMT structure.
Implementation Method 1
a buffer layer doped with p-type dopants to reduce lattice mismatch and electron injection
Implementation Method 2
a second semiconductor layer over the first semiconductor layer, wherein the second semiconductor layer has a band gap discontinuity with the first semiconductor layer
Data Source
AI summary
A high electron mobility transistor (HEMT) includes a substrate; and a first semiconductor layer over the substrate. The HEMT further includes a second semiconductor layer over the first semiconductor layer, wherein the second semiconductor layer has a band gap discontinuity with the first semiconductor layer, and at least one of the first semiconductor layer or the second semiconductor layer comprises indium. The HEMT further includes a top layer over the second semiconductor layer. The HEMT further includes a gate electrode over the top layer. The HEMT further includes a source and a drain on opposite sides of the gate electrode, wherein the top layer extends continuously from below the source, below the gate electrode, and to below the drain.