GaN HEMT Buffer Doping Segmentation for Dynamic Switching
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
GaN HEMT power devices face dynamic switching issues due to carbon impurities acting as deep level traps, leading to current collapse and increased on-state resistance, which limits their commercialization and reliability.
Innovation Solution
A compound semiconductor device with III-nitride buffer layers doped with carbon and/or iron, where the lower buffer layer has a higher average doping concentration than the upper buffer layer, enabling high breakdown voltage and fast dynamic switching by optimizing the doping concentrations through MOCVD processes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If carbon impurities are heavily doped into the GaN buffer layer to achieve high resistivity and high breakdown voltage, then the voltage blocking capability is improved, but dynamic switching performance deteriorates due to current collapse and Rdson shift
Solution Approach 1:
The patent divides the single doped buffer layer into multiple buffer layers with different doping concentrations. The lower buffer layer has high carbon doping concentration for voltage blocking, while the upper buffer layer has low or zero carbon doping to prevent carrier trapping, thus segmenting the conflicting functions spatially
Solution Approach 2:
Different regions of the buffer structure are assigned different carbon doping concentrations according to their specific functional requirements: high doping in the lower region for electrical isolation and breakdown voltage, low doping in the upper region for maintaining fast dynamic switching characteristics
2Ease of manufacture
If a single doped buffer layer is used to simplify the device structure, then manufacturing complexity is reduced, but both high breakdown voltage and fast dynamic switching cannot be achieved simultaneously
Solution Approach 1:
The buffer structure is segmented into multiple layers with distinct doping profiles, allowing each layer to optimize for its specific function while collectively achieving both high breakdown voltage and fast switching performance
Solution Approach 2:
The patent creates a composite buffer structure combining regions with different carbon doping concentrations, effectively integrating the beneficial properties of both heavily doped (high resistivity) and lightly doped (fast switching) regions into a single functional unit
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 solution achieves high breakdown voltage greater than 700V and minimizes Rdson shift from off-state to on-state resistance by less than 20%, addressing the reliability concerns and enhancing the performance of GaN HEMT power devices.
Implementation Method 1
GaN is typically grown on 150 mm or 200 mm diameter Si substrates (GaN-on-Si) using MOCVD (Metal-Organic Chemical Vapour Deposition) reactors
Implementation Method 2
At the core of GaN HEMT power devices is an AlGaN/GaN heterojunction (also called barrier/channel) that confines high mobility 2DEG (two-dimensional electron gas) along its interface
Implementation Method 3
The carbon impurities act as deep level traps which capture free carriers under high voltage stress (off-state) and lead to reduced current or higher Rdson (on-state resistance) afterwards in the on-state
Data Source
AI summary
A compound semiconductor device includes a first III-nitride buffer layer doped with carbon and/or iron, a second III-nitride buffer layer above the first III-nitride buffer layer and doped with carbon and/or iron, a first III-nitride device layer above the second III-nitride buffer layer, and a second III-nitride device layer above the first III-nitride device layer and having a different band gap than the first III-nitride device layer. A two-dimensional charge carrier gas arises along an interface between the first and second III-nitride device layers. The first III-nitride buffer layer has an average doping concentration of carbon and/or iron which is greater than that of the second III-nitride buffer layer. The second III-nitride buffer layer has an average doping concentration of carbon and/or iron which is comparable to or greater than that of the first III-nitride device layer. A method of manufacturing the compound semiconductor device is described.