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In this work, H2O-Al2O3/O3-Al2O3 insulating bilayers were grown on GaN by atomic-layer deposition (ALD) technique using H2O vapor and O3 as oxidants. The electrical and material properties show that the H2O-Al2O3/O3-Al2O3 stack structure appeared to be an appropriate dielectric for GaN MOS devices that had low leakage current densities, high breakdown voltages, and good capacitance-voltage ( C-V) curves. The H2O-Al2O3 interlayer between the O3-Al2O3 and GaN efficiently prevented the GaN surface from oxidizing by ozone oxidant by its strong oxidizing power. By taking photo-assisted C-V measurements, it was found that the deep interface state densities at the Al2O3/GaN interface reduced, while increasing the thicknesses of the H2O-Al2O3 interlayer restricted the 'Vth shift' phenomenon and improved the stability and reliability of the GaN MOS devices. [ABSTRACT FROM AUTHOR]

The influence of different AlGaN Impurity Blocking Layer (IBL) thickness in the GaN/Si (111) structure with GaN/AlN SLs buffer on the material and electrical properties of GaN/Si (111) system was studied in detail. It is found that the insertion of AlGaN IBL can increase the (102) FWHM and decrease the (002) FWHM. Meanwhile, AlGaN IBL with an optimized thickness can further improve the surface roughness and strain-state of GaN-Si (111) system. By using Secondary Ion Mass Spectroscopy, it is found that AlGaN IBL have a strong effect in blocking the Si donor impurities originating from the Si substrate during the high temperature growth, which can decrease the leakage current while the breakdown voltage can be dramatically increased. [ABSTRACT FROM AUTHOR]

In this work, the leakage current properties of semi-insulating GaN (SI-GaN) grown on Si(1 1 1) substrate with a low-temperature (LT) AlN interlayer were studied. Two terminal lateral current–voltage measurements revealed an early conduction phenomenon via buffer layers with an LT-AlN interlayer, in which both p- and n-type conduction phenomena were observed from Hall-effect measurement during temperature changing. It is suggested that the p-type conduction existed in the Si substrate due to the diffusion of Al atoms into the Si substrate during the epitaxial growth. The origin of n-type conduction was two-dimensional electron gas (2DEG) in the LT-AlN/GaN interface, which acted as a conduction channel in SI-GaN. Furthermore, the vertical leakage current measurement and the space charge limited current model were used to analyse the impact of the 2DEG conduction channel on the leakage current properties. It is revealed that leakage current properties are very sensitive to the thickness of the GaN layer above the LT-AlN interlayer (Top-GaN). Increasing the thickness of Top-GaN becomes an effective way to suppress leakage current. Therefore, both strain engineering and leakage current properties are essential factors to be considered in the selection of strain compensation interlayer in the growth of SI-GaN on Si substrate for power switching applications. [ABSTRACT FROM AUTHOR]