III-V HEMT with Oxygen-Embedded Gate Region
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Solution Overview
Problem
Developing high electron mobility transistors (HEMTs) based on III-V semiconductor compounds faces challenges in enhancing device performance, particularly in achieving high electron mobility and reducing circuit complexity, especially for enhancement-mode HEMTs which require a heterojunction structure with a thin, undoped channel layer and an intentionally doped donor-supply layer.
Innovation Solution
A method of forming a HEMT involving the epitaxial growth of a first undoped III-V compound layer on a substrate with a buffer layer, followed by a second intentionally doped III-V compound layer, creating a two-dimensional electron gas (2-DEG) at their interface. This includes depositing a dielectric passivation layer, etching through-holes, oxidizing the exposed donor-supply layer to form an oxygen-containing region, and forming a gate dielectric layer and gate electrode to achieve a normally-off operation with enhanced mobility.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a heterojunction structure with undoped channel layer and doped donor-supply layer is used to achieve high electron mobility, then carrier channel mobility is improved, but device complexity increases due to multiple material layers and doping requirements
Solution Approach 1:
The semiconductor structure is divided into distinct functional layers: an undoped channel layer for high-mobility carrier transport and a separately doped donor-supply layer for electron supply. This segmentation allows each layer to be optimized independently, with the channel layer maintaining high purity for mobility while the donor layer provides controlled doping for carrier supply.
Solution Approach 2:
Different regions of the semiconductor structure have different doping characteristics: the channel layer is intentionally kept undoped or lightly doped to maximize electron mobility, while the donor-supply layer is intentionally doped to provide electrons. This local differentiation of material properties enables simultaneous optimization of both mobility and carrier supply.
2Device complexity
If enhancement-mode HEMT structure is implemented to eliminate negative-polarity voltage supply, then circuit complexity is reduced, but achieving normally-off operation requires precise control of heterojunction properties
Solution Approach 1:
The heterojunction is designed with predetermined properties during fabrication, including specific layer thicknesses, composition gradients, and doping profiles that are established in advance. The donor-supply layer is pre-doped with controlled concentration and depth, and the channel layer is pre-configured with its undoped or lightly-doped state, ensuring the device achieves normally-off operation without requiring post-fabrication adjustments.
3Reliability
If multiple epitaxial layers with different compositions are grown to form the heterojunction, then electron mobility is enhanced, but manufacturing process complexity increases
Solution Approach 1:
The heterostructure is formed through continuous epitaxial growth processes where layers are deposited sequentially in a single fabrication run. The transition from the donor-supply layer to the channel layer is achieved through continuous compositional modulation during growth, maintaining process continuity and avoiding discrete, complex assembly steps.
Solution Approach 2:
The invention employs composite semiconductor structures combining different III-V compound materials (such as GaN, AlGaN, InGaN) with varying band gaps and material properties. These composite layers are grown epitaxially with controlled composition gradients, creating a heterojunction that leverages the advantageous properties of each material for high electron mobility while maintaining manufacturability through established epitaxial techniques.
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 approach results in a high electron mobility transistor with improved carrier channel mobility and reduced circuit complexity, enabling efficient signal transmission at high frequencies and higher operation voltages while eliminating the need for a negative-polarity voltage supply.
Implementation Method 1
epitaxially growing a first III-V compound layer having a first composition on a substrate and epitaxially growing a second III-V compound layer having a second composition different from the first composition on the first III-V compound layer
Implementation Method 2
The exposed portion of the second III-V compound layer is oxidized through the through-hole to form an oxygen containing region
Data Source
AI summary
A semiconductor structure includes a first III-V compound layer. A second III-V compound layer is disposed on the first III-V compound layer and is different from the first III-V compound layer in composition. A dielectric passivation layer is disposed on the second III-V compound layer. A source feature and a drain feature are disposed on the second III-V compound layer, and extend through the dielectric passivation layer. A gate electrode is disposed over the second III-V compound layer between the source feature and the drain feature. The gate electrode has an exterior surface. An oxygen containing region is embedded at least in the second III-V compound layer under the gate electrode. A gate dielectric layer has a first portion and a second portion. The first portion is under the gate electrode and on the oxygen containing region. The second portion is on a portion of the exterior surface of the gate electrode.