Recessed Ohmic Electrode Nitride Semiconductor Contact Resistance
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Solution Overview
Problem
Existing semiconductor devices using nitride semiconductors face inadequate reduction in contact resistance, primarily due to the trade-off between electron gas concentration and contact resistance at the heterojunction interface, limiting their performance in high-breakdown-voltage and high-speed applications.
Innovation Solution
A semiconductor device design featuring a recessed ohmic electrode with inclined contact interfaces that increase in width from the lower surface of the second nitride semiconductor layer to its upper surface, with the second contact interface being more steeply inclined than the first, allowing for reduced contact resistance and optimal two-dimensional electron gas concentration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the distance between the electrode and the 2DEG layer is reduced to lower contact resistance, then contact resistance decreases, but the electron gas concentration becomes difficult to control
Solution Approach 1:
The patent transitions from a planar contact structure to a three-dimensional recessed contact structure. The recess extends vertically into the semiconductor layer, creating multiple contact interfaces at different depths. This dimensional change allows the contact to reach the 2DEG layer formed at the heterojunction interface while maintaining control over electron gas concentration through the inclined side surfaces that provide gradual transition zones.
Solution Approach 2:
The contact structure is divided into multiple segments: a first contact interface at a higher position and a second contact interface at a lower position deeper in the recess. This segmentation allows different portions of the contact to serve different functions - the first interface provides gradual electron gas accumulation while the second interface establishes direct ohmic contact with the 2DEG layer, thereby resolving the contradiction between low contact resistance and controlled electron gas concentration.
2Reliability
If a recessed contact structure is formed to reduce contact resistance, then contact resistance decreases, but the device structure becomes more complex
Solution Approach 1:
The patent controls the geometry parameters of the recess structure, specifically the inclination angles of the side surfaces. By optimizing these angular parameters, the structure achieves effective contact resistance reduction while maintaining manufacturability. The inclined surfaces create gradual transitions that facilitate electron transport without requiring excessively complex three-dimensional geometries.
Solution Approach 2:
The recessed contact structure introduces local structural complexity only at the contact region where it is most needed for performance improvement. The rest of the device maintains conventional planar heterojunction structure. This localized approach minimizes the overall impact on device complexity while achieving the primary goal of reducing contact resistance through the specialized contact geometry.
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 design significantly reduces contact resistance by minimizing the distance between the ohmic electrode and the two-dimensional electron gas layer, enhancing the operational characteristics of nitride semiconductor devices.
Implementation Method 1
electrons resulting from the difference between the amount of spontaneous polarization of AlGaN and that of GaN and the difference between the amount of piezoelectric polarization of AlGaN and that of GaN
Data Source
AI summary
A semiconductor device includes: a second nitride semiconductor layer formed on a first nitride semiconductor layer, and having a larger band gap than the first nitride semiconductor layer; and an electrode filling a recess formed in the first and second nitride semiconductor layers. The first nitride semiconductor layer has a two-dimensional electron gas layer immediately below the second nitride semiconductor layer. The electrode and the second nitride semiconductor layer are in contact with each other at a first contact interface. The electrode and a portion of the first nitride semiconductor layer corresponding to the two-dimensional electron gas layer are in contact with each other at a second contact interface connected below the first contact interface. The first contact interface is formed such that a width of the recess increases upward. The second contact interface is more steeply inclined than the first contact interface.