Dual-Gate GaN HEMT Structure for Precise Pinch-Off Voltage Control
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Solution Overview
Problem
High-electron-mobility transistors (HEMTs), particularly those using GaN, face challenges in controlling the depletion mode pinch-off voltage, which is typically higher than -6V, necessitating improved gate control and subthreshold behavior for low voltage applications like GaN integrated circuits.
Innovation Solution
The implementation of a structure comprising a depletion mode gate and an enhancement mode gate connected together, with an isolation region between them, utilizing field plates and epitaxially grown p-type doped GaN layers, forming a metal-insulator-semiconductor (MIS) capacitor, to achieve precise control over the pinch-off voltage without additional process complexity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a conventional HEMT structure with single gate is used, then the device can operate at high frequencies, but the depletion mode pinch-off voltage cannot be controlled below -6V
Solution Approach 1:
The gate is divided into two independent gates: an enhancement mode gate and a depletion mode gate. Each gate can be independently controlled to achieve different operating modes. The enhancement mode gate provides positive threshold voltage control while the depletion mode gate provides negative threshold voltage control, enabling precise pinch-off voltage control below -6V that cannot be achieved with a conventional single gate structure.
2Measurement precision
If additional process complexity is introduced to achieve multiple threshold modes, then better voltage control is possible, but manufacturing complexity increases
Solution Approach 1:
Both enhancement mode and depletion mode gates are formed using the same field plate structure and identical semiconductor material layers (AlGaN/GaN heterostructure). The two gates share common manufacturing processes including epitaxial growth, photolithography, and metallization steps. This merging of processes achieves multiple threshold modes without significantly increasing manufacturing complexity.
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
This configuration provides significant improvement in gate control and subthreshold behavior, enabling the generation of multiple threshold depletion modes with enhanced Vt control, suitable for low voltage applications without increasing process complexity.
Implementation Method 1
forming a metal-insulator-semiconductor (MIS) capacitor
Implementation Method 2
forming at least one depletion mode gate comprising a field plate on a conductive material over a semiconductor material
Data Source
AI summary
The present disclosure relates to semiconductor structures and, more particularly, to a high-electron-mobility transistor and methods of manufacture. The structure includes: at least one depletion mode gate on a conductive material over a semiconductor material; and at least one enhancement mode gate electrically connected to the at least one depletion mode gate and over the semiconductor material.