GaN Cap Layer Quantum Well Prevents Current Collapse in HEMTs
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Solution Overview
Problem
High drain voltage applied to HEMTs with InAlN electron supply layers and SiN passivation films leads to current collapse due to electron trapping, resulting in increased on-resistance and reduced performance at high frequencies.
Innovation Solution
A semiconductor apparatus structure is developed with an InAlN electron supply layer and a SiN passivation film, where a cap layer forms a quantum well to prevent electron injection into the passivation film, maintaining 2DEG density and preventing current collapse by increasing the barrier height between the cap layer and the SiN film.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a SiN passivation film is formed over an InAlN electron supply layer to protect the device, then the insulation and protection performance is improved, but electrons are trapped by the SiN film under high drain voltage, causing current collapse and increased on-resistance
Solution Approach 1:
A cap layer formed of GaN or AlGaN is introduced as an intermediary between the InAlN electron supply layer and the SiN passivation film. This cap layer acts as a mediator that prevents direct electron injection from the InAlN layer into the SiN film, thereby eliminating the current collapse phenomenon while maintaining the protective function of the SiN passivation film.
Solution Approach 2:
The original direct interface between the InAlN electron supply layer and SiN passivation film is segmented by introducing a cap layer. This segmentation creates a two-stage barrier structure where the cap layer first blocks electrons from reaching the SiN film, preventing electron trapping and current collapse while allowing the SiN film to maintain its insulation and protection functions.
2Productivity
If InAlN is used in the electron supply layer to achieve high output and high frequency performance, then the electron density and frequency response are improved, but the susceptibility to electron trapping by the SiN passivation film increases, leading to current collapse
Solution Approach 1:
The cap layer serves as a protective intermediary that specifically addresses the high susceptibility of InAlN-based structures to electron trapping. By positioning the cap layer between the InAlN electron supply layer and the SiN passivation film, it prevents the harmful interaction while allowing the InAlN layer to maintain its superior electron density and high-frequency performance characteristics.
Solution Approach 2:
The cap layer is selectively positioned only where needed - between the InAlN electron supply layer and the SiN passivation film - to provide localized protection against electron trapping. This local quality enhancement allows the InAlN layer to maintain its high-frequency performance while specifically addressing the reliability issue in the critical interface region.
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 structure effectively prevents current collapse even under high drain voltage, maintaining on-current and reducing on-resistance, thus enhancing the high-frequency performance of HEMTs.
Implementation Method 1
A quantum well is formed by the cap layer
Implementation Method 2
piezoelectric polarization or the like is generated in AlGaN due to distortion caused by different lattice constants between AlGaN and GaN, and high-density 2DEG (Two-Dimensional Electron Gas) is generated
Data Source
AI summary
A semiconductor apparatus includes an electron transit layer formed of a nitride semiconductor over a substrate; an electron supply layer formed of a nitride semiconductor including In over the electron transit layer; a cap layer formed of a nitride semiconductor over the electron supply layer; an insulation film formed over the cap layer; a source electrode and a drain electrode formed over the electron transit layer or the electron supply layer; and a gate electrode formed over the cap layer. A quantum well is formed by the cap layer.