HEMT Dielectric Plug Modulates Surface Electric Field
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Solution Overview
Problem
III-V compound semiconductor-based transistors, such as HEMTs, face challenges in achieving high breakdown voltage due to the concentration of surface electric fields around the gate edge, which negatively affects device performance.
Innovation Solution
A novel structure for III-V compound semiconductor transistors is introduced, featuring a dielectric layer with embedded dielectric plugs between the gate and drain structures, which modulates the surface electric field and enhances breakdown voltage by reducing peak surface electric field concentrations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a metallic field plate is added over the gate structure to modulate surface electric field distribution, then breakdown voltage is enhanced, but device structure complexity increases
Solution Approach 1:
A dielectric layer is introduced as an intermediary between the gate structure and the drift region. This dielectric layer modulates the surface electric field distribution without requiring additional metallic field plates, thereby enhancing breakdown voltage while avoiding increased structural complexity. The dielectric material serves as a mediator that controls electric field concentration through its permittivity properties.
2Ease of operation
If negative bias is applied to the gate to control the depletion region, then transistor switching is enabled, but surface electric field concentration around the gate edge increases
Solution Approach 1:
The dielectric layer is selectively positioned in the drift region adjacent to the gate structure, creating local quality variation. This localized dielectric structure modifies the electric field distribution specifically in the high-stress region near the gate edge, reducing field concentration where it is most harmful, while leaving other regions unchanged to maintain normal transistor switching operation.
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 dielectric plug structure effectively reduces peak surface electric field by approximately 40%, thereby improving the breakdown voltage of III-V compound semiconductor transistors, as simulated and demonstrated in the HEMT design.
Implementation Method 1
a HEMT forms a large surface electric field around a gate edge, which affects the depletion region curve in a drift region between a gate structure and a drain
Implementation Method 2
a metallic field plate is sometimes added over or next to the gate structure over a passivation layer that is between the gate structure and the drain. The field plate modulates the surface electric field distribution
Data Source
AI summary
A high electron mobility transistor (HEMT) includes a silicon substrate, an unintentionally doped gallium nitride (UID GaN) layer over the silicon substrate. The HEMT further includes a donor-supply layer over the UID GaN layer, a gate structure, a drain, and a source over the donor-supply layer. The HEMT further includes a dielectric layer having one or more dielectric plug portions in the donor-supply layer and top portions between the gate structure and the drain over the donor-supply layer. A method for making the HEMT is also provided.