Implanted GaN Ohmic Contact Structure for Low Contact Resistance
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Solution Overview
Problem
Existing power semiconductor devices, particularly high electron mobility transistors (HEMTs), face challenges in achieving low contact resistances for high-frequency applications due to complex and costly fabrication methods associated with GaN-doped regrown ohmic contacts, which often result in non-planar contacts.
Innovation Solution
The semiconductor device incorporates a Group III-nitride semiconductor structure with a thin barrier layer and implanted regions extending through the barrier layer into the channel layer, featuring a recess for an ohmic contact, which reduces contact resistance to less than 0.15 ohm-mm without the need for GaN-doped regrown contacts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If GaN-doped regrown ohmic contacts are used, then contact resistance can be reduced, but manufacturing complexity and cost increase significantly
Solution Approach 1:
The patent extracts and eliminates the complex GaN-doped regrown fabrication step from the process. Instead of using regrown contacts, the invention uses a simple metal contact formed directly on the AlGaN barrier layer, removing the problematic intermediate growth step while maintaining low contact resistance through optimized metal composition and interface engineering
Solution Approach 2:
The patent changes the contact formation parameters by using a metal contact with specific composition (containing at least one of Ti, Mo, W, Pt, Pd, Ni, Cu, or Ag) and controlling the AlGaN barrier layer thickness (5-20 nm) and doping concentration (1×10^18 to 1×10^19 atoms/cm³), achieving low contact resistance without requiring the complex regrowth process
2Reliability
If GaN-doped regrown ohmic contacts are used, then contact resistance can be reduced, but manufacturing time and cost increase
Solution Approach 1:
The patent removes the time-consuming GaN-doped regrown step from the fabrication sequence, replacing it with a direct metal deposition process that can be performed in standard sputtering or evaporation equipment, significantly reducing manufacturing cycle time and cost
Solution Approach 2:
The patent performs preliminary doping of the AlGaN barrier layer before contact formation, creating a highly doped region that facilitates low-resistance contact. This preliminary action eliminates the need for subsequent regrowth steps, streamlining the process and improving productivity
3Reliability
If GaN-doped regrown ohmic contacts are used, then contact resistance can be reduced, but non-planar contact formation occurs
Solution Approach 1:
The patent extracts and eliminates the regrowth process that causes non-planar contact formation. By forming the metal contact directly on the planar AlGaN barrier layer surface through deposition, the contact maintains planarity while achieving low resistance through the highly doped interface region
Solution Approach 2:
The patent creates local quality enhancement by forming a highly doped region specifically at the contact interface (1×10^18 to 1×10^19 atoms/cm³) while maintaining the overall planar structure. This localized doping provides low resistance without disrupting the planar morphology of the contact surface
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 achieves significantly lower contact resistances, enhancing power added efficiency and operating characteristics at higher frequencies while avoiding the drawbacks of regrown GaN ohmic contacts, such as increased manufacturing time and cost, and non-planar contact formation.
Implementation Method 1
The semiconductor device includes an implanted region extending into the channel layer. The implanted region includes a distribution of implanted dopants.
Implementation Method 2
The semiconductor device includes an ohmic contact within the recess. A contact resistance of the ohmic contact with the Group III-nitride semiconductor structure is about 0.15 ohm-mm or less.
Data Source
AI summary
Semiconductor devices with reduced contact resistance of ohmic contacts are provided. In one example, the semiconductor device includes a Group III-nitride semiconductor structure. The Group III-nitride semiconductor structure includes a channel layer and a barrier layer on the channel layer. The semiconductor device includes an implanted region extending into the channel layer. The implanted region includes a distribution of implanted dopants. The semiconductor device includes a recess in the implanted region. The recess extends through the barrier layer into the channel layer. The semiconductor device includes an ohmic contact within the recess.