GaN HEMT Drain Doping to Prevent Back Gating
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Solution Overview
Problem
GaN-based high electron mobility transistors (HEMTs) suffer from a back gating effect, where a depletion region forms under the drain contact structure due to a relative negative bias, leading to potential failure, especially in p-GaN based enhancement mode HEMTs.
Innovation Solution
Incorporating a highly-doped implantation region in the HEMT design, positioned in the drain access region, which increases the electron density under and/or below the drain contact structure, thereby preventing the extension of the depletion region towards the drain contact structure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a GaN-based HEMT is operated with a relative negative bias under the drain contact structure, then the device can achieve normal transistor operation and switching function, but a depletion region forms and extends towards the drain contact structure causing back gating effect and potential device failure
Solution Approach 1:
The patent introduces a highly-doped implantation region specifically in the drain access region, creating a localized area with different doping characteristics. This highly-doped region modifies the local electrical properties to prevent depletion region extension, thereby eliminating the back gating effect while maintaining normal transistor operation elsewhere in the device.
Solution Approach 2:
The highly-doped implantation region is formed during the fabrication process before the device is operated. This preliminary doping action pre-establishes a protective region that prevents the formation and extension of depletion regions during subsequent operation, thereby preventing the back gating effect before it can occur.
2Power
If the depletion region is allowed to extend under the drain contact structure, then the transistor can achieve higher voltage operation, but the back gating effect causes increased ON resistance and potential device failure
Solution Approach 1:
The highly-doped implantation region creates a localized modification in the drain access region that specifically addresses the depletion region extension problem. This local doping enhancement prevents the harmful back gating effect while allowing the rest of the device to maintain its voltage operation capabilities.
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 highly-doped implantation region effectively prevents the depletion region from extending to the drain contact structure, enhancing the reliability and performance of GaN-based HEMTs by reducing the risk of failure and improving ON resistance.
Implementation Method 1
implanting a dopant to form a first doped region extending from the top side into the GaN layer in a drain access region
Data Source
AI summary
In some examples, a transistor comprises a gallium nitride (GaN) layer; a GaN-based alloy layer having a top side and disposed on the GaN layer, wherein source, drain, and gate contact structures are supported by the GaN layer, and a first doped region positioned in a drain access region and extending from the top side into the GaN layer.