GaN HEMT Rear Electrode Layout for Hole Extraction
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
In AlGaN/GaN high electron mobility transistors (HEMTs), the accumulation of holes generated by impact ionization in the electron transit layer leads to reduced withstand voltage and the Kink effect, which is difficult to address due to the challenge of effectively extracting holes from the layer without degrading high-frequency performance and increasing capacitance.
Innovation Solution
A compound semiconductor device is designed with a substrate having an opening from the rear side, a compound semiconductor layer with a local p-type region exposed at the end of the opening, and a rear electrode connected to the p-type region, allowing for effective extraction of holes generated by impact ionization without increasing capacitance or chip area.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a hole extraction electrode is provided on the rear surface of the p-type GaN layer, then holes can be extracted from the electron transit layer, but the entire rear surface is covered with an electrically conductive layer which generates capacitance and degrades high-frequency performance
Solution Approach 1:
The patent applies local quality by forming a p-type region only in the specific area where the opening is located, rather than making the entire rear surface conductive. This localized doping approach allows hole extraction to occur only at the necessary position while leaving other areas non-conductive, thus avoiding unwanted capacitance effects and preserving high-frequency performance.
Solution Approach 2:
The patent segments the conductive region by creating a discrete p-type region within the electron transit layer that is exposed through an opening. Instead of a continuous conductive layer covering the entire rear surface, the conductive path is divided and confined to a specific segmented area, reducing parasitic capacitance while maintaining hole extraction functionality.
2Reliability
If a high electric field is applied between the drain electrode and the hole extraction electrode, then holes can be extracted effectively, but the withstand voltage is reduced
Solution Approach 1:
The patent introduces a vertical dimension by forming an opening through the substrate to access the electron transit layer from the rear side. This three-dimensional approach allows the hole extraction electrode to be positioned in a different spatial dimension, enabling effective hole extraction through the vertical field while distributing the electric field in a way that maintains lateral breakdown voltage.
3Area of stationary object
If the electron transit layer is made thin to reduce device size, then integration density increases, but hole extraction becomes less effective
Solution Approach 1:
The patent introduces a p-type region as an intermediary layer between the electron transit layer and the hole extraction electrode. This intermediate p-type region, exposed through the opening, serves as a collection point for holes generated in the thin electron transit layer, enhancing extraction efficiency even when the electron transit layer thickness is reduced for smaller device size.
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 design enhances the withstand voltage and reliability of AlGaN/GaN HEMTs by efficiently extracting and discharging holes, preventing capacitance increase and breakdown, while maintaining high-frequency performance.
Implementation Method 1
holes generated by impact ionization in a high-electric field
Implementation Method 2
distortion occurs in the AlGaN layer due to the difference in lattice constant between GaN and AlGaN. This causes piezoelectric polarization
Implementation Method 3
if holes generated by impact ionization in a high-electric field are accumulated in the electron transit layer
Data Source
AI summary
A compound semiconductor device includes a substrate having an opening formed from the rear side thereof; a compound semiconductor layer disposed over the surface of the substrate; a local p-type region in the compound semiconductor layer, partially exposed at the end of the substrate opening; and a rear electrode made of a conductive material, disposed in the substrate opening so as to be connected to the local p-type region.