HEMT Ohmic Contact via N-Doped GaN Layer
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Solution Overview
Problem
High temperature processes used for forming ohmic contacts in high electron mobility transistors (HEMTs) can damage other semiconductor layers, limiting the effectiveness of the device.
Innovation Solution
A high electron mobility transistor design that forms ohmic contact without a high temperature process, using a contact layer made of n-type doped Group III-V compound semiconductor, with a recessed gate electrode and undoped GaN layer between the contact and channel supply layers, reducing contact resistance and minimizing layer damage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a high temperature process is used to form ohmic contact between source/drain electrodes and channel supply layer, then contact resistance is reduced, but other semiconductor layers are damaged
Solution Approach 1:
An n-type doped contact layer is introduced as an intermediary layer between the channel supply layer and the source/drain electrodes. This contact layer serves as a mediator that enables ohmic contact formation at lower temperatures, preventing direct high-temperature exposure to the channel supply layer and other sensitive semiconductor layers, thus reducing contact resistance without causing layer damage
Solution Approach 2:
The contact layer is heavily doped with silicon (Si) to achieve a high doping concentration (e.g., 1×10^19 to 1×10^21 atoms/cm³), which fundamentally changes the electrical parameters of the contact region. This parameter change enables the formation of low-resistance ohmic contacts at reduced processing temperatures, resolving the contradiction between contact quality and layer integrity
2Device complexity
If the channel supply layer directly contacts the source and drain electrodes, then device structure is simplified, but contact resistance increases and requires high temperature processing
Solution Approach 1:
The n-type doped contact layer acts as an essential intermediary between the channel supply layer and source/drain electrodes, providing a low-resistance pathway for current flow. While this adds a layer to the structure, it significantly improves contact reliability and enables lower temperature processing, representing a worthwhile trade-off in device design
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
Enables the formation of ohmic contact in HEMTs without high temperature processing, reducing damage to semiconductor layers and improving electron mobility by using n-type doped contact layers and undoped GaN layers, enhancing the device's operational efficiency and reliability.
Implementation Method 1
The contact layer is configured to form an ohmic contact on the channel layer
Implementation Method 2
The contact layer is n-type doped
Implementation Method 3
a channel layer including a 2-dimensional electron gas (2DEG)
Data Source
AI summary
According to example embodiments, a high electron mobility transistor includes: a channel layer including a 2-dimensional electron gas (2DEG); a contact layer on the channel layer; a channel supply layer on the contact layer; a gate electrode on a portion of the channel layer; and source and drain electrodes on at least one of the channel layer, the contact layer, and the channel supply layer. The contact layer is configured to form an ohmic contact on the channel layer. The contact layer is n-type doped and contains a Group III-V compound semiconductor. The source electrode and the drain electrode are spaced apart from opposite sides of the gate electrode.