GaN Semiconductor Structure for Normally-Off Operation
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Solution Overview
Problem
III-nitride based semiconductor structures face challenges in achieving normally-off operation due to the presence of two-dimensional electron gas, which complicates electronic properties and can be damaged by conventional manufacturing methods like plasma etching.
Innovation Solution
A semiconductor structure with a first GaN layer including p-type GaN and a second GaN layer with distinct doping concentrations, where the second region outside the gate electrode has a higher doping concentration, eliminating two-dimensional electron gas under the gate electrode and allowing for normally-off operation without damaging the structure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If plasma etching process is used to recess the gate electrode, then the normally-off operation can be achieved, but the surface of the structure layer is damaged and electronic properties are jeopardized
Solution Approach 1:
The patent changes the doping concentration parameter of the GaN layer to achieve normally-off operation. By setting the doping concentration of the second GaN layer to be less than 1×10^16 cm^-3, the patent eliminates the need for plasma etching while maintaining electronic properties, thus resolving the contradiction between ease of operation and reliability
2Ease of operation
If p-type GaN layer is added to the underneath of the gate electrode, then the normally-off operation can be achieved, but the distance between the two-dimensional electron gas and the gate electrode increases and transconductance deteriorates
Solution Approach 1:
The patent changes the doping concentration parameter of the existing second GaN layer instead of adding a new p-type layer. By adjusting the doping concentration to be less than 1×10^16 cm^-3, the patent achieves normally-off operation while keeping the gate electrode at its original position, thus maintaining transconductance and avoiding the contradiction
3Ease of operation
If the doping concentration of the second GaN layer is reduced, then the two-dimensional electron gas is eliminated for normally-off operation, but the electron mobility and carrier concentration are affected
Solution Approach 1:
The patent applies local quality by having different doping concentrations in different regions. The second GaN layer has a low doping concentration (<1×10^16 cm^-3) in the gate region to eliminate 2DEG for normally-off operation, while other regions can have different doping levels to maintain electron mobility and carrier concentration where needed
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 structure enables excellent electronic properties and reliable normally-off operation without damaging the semiconductor layers, maintaining high electron mobility and transconductance, suitable for high-energy electronic devices like high-voltage and RF elements.
Implementation Method 1
a first GaN layer disposed above the buffer layer and comprising p-type GaN; a second GaN layer disposed on the first GaN layer and comprising a first region and a second region. The first region of the second GaN layer is positioned correspondingly to the gate electrode and comprises n-type GaN having a first doping concentration
Implementation Method 2
The III-nitride based semiconductor structure (such as III-nitride based HEMT) has strong polarization and piezoelectric effects, and will therefore generate two-dimensional electron gas (2DEG) having high density of carriers
Implementation Method 3
The III-nitride based semiconductor structure (such as III-nitride based HEMT) has strong polarization and piezoelectric effects, and will therefore generate two-dimensional electron gas (2DEG) having high density of carriers
Data Source
AI summary
A III-nitride based semiconductor structure includes a substrate; a buffer layer disposed above the substrate; a first gallium nitrite (GaN) layer disposed above the buffer layer and including p-type GaN; a second GaN layer disposed on the first GaN layer and including at least a first region and a second region; a channel layer disposed above the second GaN layer; a barrier layer disposed above the channel layer; and a gate electrode disposed above the barrier layer. The first region of the second GaN layer is positioned correspondingly to the gate electrode and includes n-type GaN having a first doping concentration. The second region of the second GaN layer (such as the lateral portion of the second GaN layer) is positioned correspondingly to the areas outsides the gate electrode and includes n-type GaN having a second doping concentration larger than the first doping concentration.