GaN HEMT p-type diffusion region leakage current suppression
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Solution Overview
Problem
High electron mobility transistors (HEMTs) with gallium nitride (GaN) suffer from leakage current issues due to thick electron transit layers, which affect amplification efficiency and are prone to a normally-on status, making it difficult to achieve a normally-off characteristic while maintaining crystallinity and electron mobility.
Innovation Solution
A semiconductor device structure with a p-type diffusion region formed beneath the gate electrode, using a growth control layer to prevent Mg diffusion into the electron transit layer, allowing for a normally-off status and reduced leakage current by increasing resistance and suppressing two-dimensional electron gas formation directly beneath the gate.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If the electron transit layer is made thick to secure crystallinity, then the crystallinity is improved, but leakage current increases and amplification efficiency decreases
Solution Approach 1:
The patent introduces a p-type diffusion region specifically in the lower part of the electron transit layer directly beneath the gate electrode, creating a localized region with different electrical properties (higher resistance, p-type conductivity) while maintaining the overall n-type character and thickness of the electron transit layer for crystallinity. This local modification suppresses leakage current without compromising the bulk crystalline structure.
2Stability of the object's composition
If the electron transit layer is made thick to secure crystallinity, then the crystallinity is improved, but amplification efficiency decreases
Solution Approach 1:
By creating a localized p-type diffusion region only in the lower part beneath the gate electrode, the patent maintains the thick electron transit layer structure needed for crystallinity while locally suppressing leakage current to improve amplification efficiency. The rest of the electron transit layer retains its high electron mobility characteristics.
3Object-generated harmful factors
If Mg is doped into the lower part of the electron transit layer to increase resistance and suppress leakage current, then leakage current is reduced, but Mg diffusion into the electron transit layer degrades device characteristics
Solution Approach 1:
The patent segments the electron transit layer into distinct regions: a lower part containing the p-type diffusion region with Mg impurities, and an upper part free from Mg diffusion. This segmentation is achieved by controlling the diffusion depth and creating a clear boundary, allowing the lower region to suppress leakage current while protecting the upper region that carries the main electron transport function.
Solution Approach 2:
The p-type diffusion region is created with localized properties (higher resistance, p-type conductivity) only in the lower part beneath the gate electrode, while the upper part of the electron transit layer maintains its original n-type character and high electron mobility. This local differentiation allows leakage suppression without degrading overall device characteristics.
4Length of stationary object
If the electron transit layer is thick, then the electric field from the gate electrode cannot reach the lower part, but this facilitates leakage current generation
Solution Approach 1:
The p-type diffusion region acts as an intermediary layer between the gate electrode and the lower part of the electron transit layer. It provides a high-resistance barrier that blocks leakage current paths while allowing the electric field to still penetrate and control the main electron transport region. The p-type region mediates between the gate control field and the leakage current suppression requirement.
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 effectively suppresses leakage current and maintains a normally-off status in HEMTs, enhancing amplification efficiency and compatibility with other semiconductor devices by controlling the resistance and crystallinity of the electron transit layer.
Implementation Method 1
the second semiconductor layer includes an impurity diffusion region in which an impurity element contained in the first semiconductor layer is diffused
Implementation Method 2
the impurity element causes the impurity diffusion region to be a p-type impurity diffusion region
Implementation Method 3
using a growth control layer to prevent Mg diffusion into the electron transit layer
Implementation Method 4
when the AlGaN/GaN heterostructure is formed, piezoelectric polarization may be induced by lattice strain between the AlGaN and GaN
Implementation Method 5
a highly-concentrated two-dimensional electron gas (2DEG) may be generated near an interface of the GaN layer serving as a channel
Data Source
AI summary
A semiconductor device includes a first semiconductor layer formed on a substrate, the first semiconductor containing an impurity element; a second semiconductor layer formed on the first semiconductor layer; a third semiconductor layer formed on the second semiconductor layer; and a gate electrode, a source electrode and a drain electrode that are formed on the third semiconductor layer. In the semiconductor device, the second semiconductor layer includes an impurity diffusion region in which an impurity element contained in the first semiconductor layer is diffused, the impurity diffusion region being located directly beneath the gate electrode and being in contact with the first semiconductor layer, and the impurity element causes the impurity diffusion region to be a p-type impurity diffusion region.