Ferroelectric ScAlN Barrier for Switchable p-FET and n-FET Channels
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Solution Overview
Problem
Current silicon-based semiconductor devices face limitations in high power electronics due to silicon's limited critical electric field and high resistance, making them unsuitable for high power applications, and III-N semiconductor devices struggle with defect control and lattice mismatch issues, particularly with incorporating high indium concentrations in InxGa1−xN alloys.
Innovation Solution
A single channel layer based III-N semiconductor device with a Scandium-doped Aluminum Nitride (ScAlN) barrier layer that can switch between p-FET and n-FET operation by reversing the polarization direction with an external electric field, allowing for the formation of 2-dimensional electron or hole gases at the interface, enabling efficient charge carrier control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If silicon-based semiconductor devices are used, then manufacturing maturity and reliability are improved, but device size increases and operating frequency is limited
Solution Approach 1:
The patent changes the semiconductor material parameter from silicon to III-Nitride materials (GaN, InGaN), which inherently possess higher critical electric fields and lower on-resistances. This material parameter change enables smaller device size while maintaining reliability, directly resolving the contradiction between device reliability and size.
Solution Approach 2:
The patent employs composite material structures including GaN/InGaN heteroepitaxial layers and ScAlN barrier layers. These composite structures leverage the advantageous properties of each material (wide bandgap of GaN, high mobility of InGaN, ferroelectricity of ScAlN) to achieve both small size and high reliability simultaneously.
2Power
If III-Nitride materials are used, then device performance and power handling capability are improved, but defect control becomes difficult
Solution Approach 1:
The patent applies local quality by introducing Scandium-doped AlN (ScAlN) barrier layers at specific interfaces where defect control is most critical. The ScAlN layer locally modifies the interface properties to suppress dislocation propagation and enhance crystal quality, thereby improving reliability while maintaining the high power handling capability of the overall III-Nitride device.
Solution Approach 2:
The ScAlN barrier layer acts as an intermediary between the GaN channel layer and the substrate or other layers. This intermediate layer mediates the interface between dissimilar materials, reducing lattice mismatch and dislocation density, thus improving defect control while preserving the high power handling capability of the III-Nitride material system.
3Speed
If indium is incorporated into InxGa1−xN alloys, then electron mobility and saturation drift rate are improved, but phase separation and lattice mismatch occur
Solution Approach 1:
The patent carefully controls the indium composition parameter x in InxGa1−xN to remain within the stable phase region (typically x < 0.35). By optimizing this parameter, the patent achieves high electron mobility and saturation drift rate while preventing phase separation, thus resolving the contradiction between speed and compositional stability.
Solution Approach 2:
The ScAlN barrier layer serves as an intermediary that suppresses misfit dislocations and phase separation at the InGaN/GaN interface. This intermediate layer stabilizes the InxGa1−xN alloy composition by preventing indium segregation, thereby maintaining phase stability while enabling high indium content for enhanced electron mobility and saturation drift rate.
4Adaptability or versatility
If a single channel layer is used for both p-FET and n-FET modes, then device versatility is improved, but charge carrier control becomes challenging
Solution Approach 1:
The patent introduces dynamic control mechanisms using ScAlN barrier layers with ferroelectric properties. By applying external electric fields, the polarization direction of the ScAlN layer can be switched, which dynamically changes the band structure at the interface to control whether electrons or holes are the majority carriers. This dynamic switching enables a single channel layer to function as both p-FET and n-FET with ease of operation.
Solution Approach 2:
The patent utilizes the ferroelectric property of ScAlN to change the polarization parameter by applying external electric fields. This parameter change in the barrier layer's polarization state directly controls the charge carrier type in the channel layer, enabling versatile operation as both p-FET and n-FET while maintaining easy control over charge carrier priority.
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
Enables the semiconductor device to operate as both p-FET and n-FET with high switching speed and reduced circuit area, overcoming the limitations of silicon-based devices and III-N semiconductor device challenges, such as defect control and lattice mismatch, by leveraging the ferroelectric properties of ScAlN for efficient charge carrier management.
Implementation Method 1
The barrier layer is a III-Nitride compound layer, e.g., Scandium-doped Aluminum Nitride (ScAlN) layer. The ScAlN material has ferroelectricity characteristic. Ferroelectricity is a characteristic of materials that have a spontaneous electric polarization that can be reversed by application of an external electric field.
Implementation Method 2
epitaxial layers grown on substrates like Sapphire, GaN, or SiC using Molecular Beam Epitaxy
Data Source
AI summary
The present disclosure discloses a semiconductor device comprising a plurality of epitaxial layers including a barrier layer and a channel layer such that two-dimensional carrier densities are formed at an interface of the barrier layer and the channel layer, wherein a priority of charge carriers of the channel layer is based on a polarization direction of the barrier layer, and wherein the polarization direction of the barrier layer can be changed by applying an electric field across the barrier layer. The semiconductor device further comprises a first source terminal and a second source terminal, wherein in one of the first source terminal and the second source terminal is ohmic to electrons and other one is ohmic to holes. The semiconductor device further comprises a first drain terminal and a second drain terminal, a gate terminal, and a set terminal ohmic to the channel layer.