GaN HEMT Back-Side Field Plate for Electric Field Control
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Solution Overview
Problem
Gallium nitride (GaN) semiconductor devices face challenges in managing high electric fields, with existing top-side field plates being less effective compared to both top-side and back-side field plates used in silicon power devices, necessitating improved electric field management techniques.
Innovation Solution
The use of patterned regions of differing conductivity under GaN devices, such as a GaN high electron mobility transistor (HEMT), where a patterned layer of oxidized silicon is formed superjacent a layer of silicon dioxide during heteroepitaxy, enabling back-side electric field management by making the silicon layer conductive as a back-side field plate.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If top-side field plates are used in GaN devices, then some electric field management is achieved, but effectiveness is reduced compared to silicon power devices that use both top-side and back-side field plates
Solution Approach 1:
The patent applies inversion by implementing the field plate function on the back-side of the GaN device rather than only on the top-side. The silicon layer is formed beneath the GaN heterostructure and selectively oxidized to create an insulating region that provides field management functionality from the opposite side, thereby achieving more effective electric field control while maintaining relatively simple device structure
Solution Approach 2:
The patent transitions from single-sided (top-side) field management to dual-sided (top-side and back-side) field management by adding functionality in the vertical dimension. The back-side field plate is formed at a different spatial location (beneath the GaN layer) to provide additional electric field control capability that complements the top-side field plate
2Reliability
If a silicon layer is formed and oxidized to create a back-side field plate, then electric field management is improved, but manufacturing process complexity increases
Solution Approach 1:
The silicon layer is formed and positioned beneath the GaN heterostructure during the epitaxial growth process, before final device fabrication steps. The selective oxidation is then performed to convert the silicon layer into silicon dioxide in specific regions, creating the back-side field plate structure in advance of subsequent device processing steps
Solution Approach 2:
The silicon layer serves as an intermediary material that is introduced between the substrate and the GaN heterostructure. This intermediate layer is selectively oxidized to form silicon dioxide regions that provide the desired electrical insulation and field management functionality, acting as a mediator to achieve the back-side field plate effect
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 effectively manages high electric fields in GaN devices, reducing circuit complexity and enhancing the performance of GaN-based transistors by creating a patterned, higher conductivity region that acts as a back-side field plate, improving the control of electric fields and device reliability.
Implementation Method 1
a patterned layer of oxidized silicon can be formed superjacent a layer of silicon dioxide
Implementation Method 2
implanting a material in the crystal lattice layer
Implementation Method 3
during or prior to the heteroepitaxy of GaN or another semiconductor material
Implementation Method 4
The two-dimensional electron gas (2DEG) channels formed by GaN based heterostructures generally have high electron mobility
Data Source
AI summary
Electric field management techniques in GaN based semiconductors that utilize patterned regions of differing conductivity under the active GaN device, such as a GaN high electron mobility transistor (HEMT), are described. As an example, a patterned layer of oxidized silicon can be formed superjacent a layer of silicon dioxide during or prior to the heteroepitaxy of GaN or another semiconductor material. These techniques can be useful for back-side electric field management because a silicon layer, for example, can be made conductive to act as a back-side field plate.