| Summary: | 碩士 === 國立交通大學 === 光電工程研究所 === 106 === Recent progress in high power field-effect transistors (FETs) was focused on GaN-based wide band-gap (WBG) semiconductors. Recent progress in high power fieldeffect
transistors (FET) focused on GaN-based wide band-gap semiconductors. GaN-based high electron mobility transistor (HEMTs) have demonstrated great potential due
to their high breakdown electric field, low on-state resistance (Ron) and high thermal stability. Therefore, GaN-based HEMT provides significantly better performances
compared with traditional Si-based power device, leading to a smaller device area as well as cost reduction. However, high defect densities and surface damages under the device process result in unreliable device performance of GaN HEMTs during high power switching. Therefore, it is essential to improve device performance through fabrication process or epitaxial technology.
In this thesis, we report two methods to improve device performance and reliability. In the first part, we report a surface passivation technology by plasma enhanced atomic layer deposition (PEALD). Prior to deposit dielectric layer on GaN HEMTs, the H2/NH3 plasma pre-treatment was employed to remove the native gallium
oxide. Following the in-situ ALD-AlN/Al2O3 was deposited and passivated the surface, leading to a 22.1% of current collapse. The surface passivated HEMT enabled a breakdown voltage to 687 V at high temperature (150oC), promising a good thermal reliability under high power operation. In the second part, we report a GaN HEMT with MOCVD-grown in-situ SiNx. The in-situ SiNx passivated the GaN surface, leading to a 7% of current collapse. Furthermore, the breakdown voltage (BV) can be increased to 400 V, promising a good stability under high voltage operation.
We can improve the current collapse and the breakdown voltage through these two methodologies. These approaches can be applied to develop novel power electronic devices with high performance, yielding a device that is reliable in power device applications.
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