GaN HEMT Charge Compensation for Normally-Off Operation
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Solution Overview
Problem
Existing nitride-based high electron mobility transistors (HEMTs) face challenges in forming reliable normally-off transistors without increasing device resistance and achieving avalanche breakdown voltage, which are crucial for high-efficiency and rugged power electronics applications.
Innovation Solution
The development of HEMT structures with p-type charge-compensation regions below the gate electrode, which preserve the two-dimensional electron gas (2DEG) channel and enable avalanche breakdown, thereby maintaining low device resistance and enhancing ruggedness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional methods are used to form normally-off transistors, then the transistor achieves normally-off operation, but the device resistance increases
Solution Approach 1:
The patent introduces p-type charge-compensation regions at specific locations below the gate electrode, rather than uniformly modifying the entire device structure. This localized approach compensates for positive charges in the barrier layer only in the gate region, preserving 2DEG channels in other regions and maintaining low device resistance while achieving normally-off operation
Solution Approach 2:
The p-type charge-compensation regions act as intermediary structures that neutralize the effect of positive charges in the barrier layer. These compensation regions provide negative charges that balance the positive charges, enabling control of the 2DEG channel without requiring complete depletion or modification of the channel structure, thus avoiding resistance increase
2Speed
If nitride HEMT structures are designed for high electron mobility, then electron mobility increases, but avalanche breakdown capability is lost
Solution Approach 1:
The patent creates different functional regions with distinct properties: the gate region contains p-type charge-compensation regions for normally-off operation, while other regions maintain the original high-mobility 2DEG channel structure. This spatial differentiation allows the device to exhibit both high electron mobility in the channel and avalanche breakdown capability through controlled charge compensation in the gate region
Solution Approach 2:
The patent modifies the charge distribution parameters locally by introducing p-type doping in the charge-compensation regions. This changes the electrical parameters (charge density, potential distribution) in the gate region without fundamentally altering the material composition or band structure of the entire device, thereby preserving high electron mobility while enabling avalanche breakdown
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
These structures allow for normally-off operation with preserved 2DEG channel electron concentrations at low gate bias, achieving improved resistance and avalanche breakdown capabilities, addressing the limitations of existing nitride HEMTs.
Implementation Method 1
a plurality of charge-compensation regions below the gate electrode, wherein the charge-compensation regions comprise a p-type material and extend through the barrier layer and at least partially through the III-V semiconductor layer
Implementation Method 2
a two dimensional electron gas (2DEG) is formed at a heterointerface between the III-V semiconductor layer and the barrier layer
Implementation Method 3
A second problem with existing nitride-based high electron mobility transistors is the realization of rugged breakdown voltage with avalanche capability
Data Source
AI summary
A variety of high electron mobility transistor structures are provided having charge compensation regions that can extend below the gate electrode through the barrier layer and at least partially through the III-V semiconductor layer. The charge compensation regions include a p-type semiconductor or oxide. In some aspects, the charge compensation regions extend vertically through said barrier layer into said channel layer, wherein said charge-compensation regions are doped with p-type dopants and are placed aside the 2DEG channel and do not overlap vertically with the 2DEG channel. In some aspects, at least a portion of the charge compensation regions extend from below the gate electrode to make Ohmic contact with the source electrode. In some aspects, by extending the charge compensation regions from below the gate electrode and closer to the source and drain electrodes, the HEFTs can demonstrate avalanche characteristics. The HEMTs can include any suitable III-V semiconductor, and in particular can include a GaN semiconductor.