GaN HEMT Floating Structures for Dynamic Ron Reduction
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Solution Overview
Problem
AlGaN/GaN high electron mobility transistors (HEMTs) face dynamic Ron or current collapse due to electron trapping at high voltage stress, leading to increased on-state resistance and leakage currents, which existing solutions like metal field plates and hole injection mechanisms fail to fully address without compromising breakdown voltage or introducing additional leakage.
Innovation Solution
A III-nitride semiconductor based heterojunction device with a p-type injector and floating structures that are not hardwired to any terminal, allowing for steady-state and transient hole injection to passivate traps and reduce electric field peaks around the gate structure, thereby preventing 2DEG depletion and minimizing leakage currents.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If metal field plates are used to reduce electric field peaks, then dynamic Ron is reduced, but breakdown voltage is compromised
Solution Approach 1:
A p-type injector layer is introduced as an intermediary structure between the gate and drain terminals. This layer mediates the electric field distribution by providing a controlled hole injection mechanism that reduces field peaks without the excessive field confinement caused by metal field plates, thereby maintaining breakdown voltage while reducing dynamic Ron.
Solution Approach 2:
The invention changes the electrical parameters of the region near the gate-drain junction by introducing a p-type doped layer. This parameter change enables controlled hole injection that dynamically adjusts the electric field distribution during operation, reducing field peaks and dynamic Ron while preserving the high-field breakdown characteristics through appropriate doping concentration and layer thickness control.
2Reliability
If hole injection mechanisms are used to passivate traps, then on-state resistance is reduced, but leakage currents are introduced
Solution Approach 1:
The p-type injector layer provides a dynamic hole injection mechanism that activates only under specific bias conditions (when the device is in off-state or during switching transitions). During normal on-state operation, the injection is naturally suppressed, preventing continuous leakage currents while still providing trap passivation when needed to reduce on-state resistance.
Solution Approach 2:
The hole injection occurs periodically during switching transitions and off-state periods rather than continuously. This periodic action allows trap passivation to reduce on-state resistance while limiting total injected charge to prevent excessive leakage, as the injection is confined to specific operational phases.
3Device complexity
If p-type injector is hardwired to drain terminal, then hole injection control is simplified, but leakage current increases at high voltages
Solution Approach 1:
The p-type injector layer is designed to be self-regulating through its doping profile and spatial positioning. The hole injection is automatically controlled by the local electric field conditions without requiring external hardwiring to the drain terminal. The injector naturally activates when and where needed based on field distribution, providing self-service control that prevents excessive leakage while maintaining simplicity.
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 solution effectively reduces dynamic Ron and on-state resistance while maintaining high breakdown voltage and reducing leakage currents, especially at high voltages, by using floating structures to manage electric fields and inject holes effectively without hardwiring to external electrodes.
Implementation Method 1
Hot carrier injection in the passivation layer, next to the gate (the control terminal) also may play a role
Implementation Method 2
the piezopolarization charge present at the AlGaN/GaN heterostructure
Implementation Method 3
the use of an Aluminium Gallium Nitride (AlGaN)/GaN heterostructure also allows the formation of a two-dimensional electron gas (2DEG) at the hetero-interface where carriers can reach very high mobility
Implementation Method 4
A III-nitride semiconductor based heterojunction device with a p-type injector and floating structures that are not hardwired to any terminal, allowing for steady-state and transient hole injection to passivate traps and reduce electric field peaks around the gate structure
Data Source
AI summary
A heterojunction device, includes a substrate (4); a Ill-nitride semiconductor region located longitudinally above or over the substrate and including a heterojunction having a two-dimensional carrier gas; first (8) and second (9) laterally spaced terminals operatively connected to the semiconductor; a gate structure (11) of first conductivity type located above or longitudinally over the semiconductor region and laterally spaced between the first and second terminals; a control gate terminal (10) operatively connected to the gate structure, a potential applied to the control gate terminal modulates and controls a current flow through the carrier gas between the terminals, the carrier gas being a second conductivity type; an injector of carriers (101) of the first conductivity type laterally spaced away from the second terminal; and a floating contact layer (102) located over the carrier gas and laterally spaced away from the second terminal and operatively connected to the injector and the semiconductor region.