SMF C3NiT: Passivation of GaN Epi-Wafers for RF and Power Devices

Important results from the project

SiN and epi a pretreated with high-temperature NH3 to reduce the trap states. Different SiN growth conditions have been fabricated. The interface between LPCVD and MOCVD have been studied. SiN characterization was performed on all samples including the refractive index and thin-film strain. The Ga binding energy at the interface of SiN and epi was characterized. The transistors were fabricated on samples with LPCVD SiN, while the transistors on samples with MOCVD SiN are ongoing. Trapping effects were characterized on the samples with LPCVD SiN.

Expected long term effects

The optimized surface pretreatment indicates that the surface of epi is required to be controlled. Moreover, the refractive index is not enough to define the properties of SiN since the SiN layers grown by MOCVD and LPCVD show completely different Ga binding energy. In other words, the SiN growth mechanism is more critical. The device results of different Si composition LPCVD SiN are in line with literature that Si-rich tends to have fewer traps.

Approach and implementation

Based on current results and literature survey, the SiN growth mechanism, thin film strain, epi strain, and the binding energy of different atoms (Ga, O, H, and N) are believed to be critical to the performance of the SiN passivation. Different SiN growth mechanisms impact the interface properties and composition. The SiN strain will modify the epi strain, resulting in modified electrical properties. Different epi-wafers with different internal strain require different SiN to match. Once the impact of different atoms´ binding energy can be controlled, the trap states can be reduced.