Franky Lumbantoruan

Investigation of TMAl preflow to the properties of AlN and GaN film grown on Si(111) by MOCVD

The influence of TMAl preflow to the AlN buffer layer and GaN thin film was studied by Optical Microscope, Atomic Force Microscope, X-ray diffraction and Transmission Electron Microscope. Different duration of TMAl preflow lead to substantially differences of the AlN buffer layer and GaN film properties in terms of surface morphology and crystal quality. It was found without TMAl preflow the crystal quality of AlN buffer layer and GaN deteriorated due to the formation of amorphous interlayer between Si and AlN. Meltback etching and cracks was observed on the surface of GaN grown on AlN without TMAl preflow. However, overlong duration of TMAl preflow degraded the properties of AlN buffer layer and the subsequent GaN layer. GaN grown with longer TMAl preflow suffer of poor crystal quality, high density cracks and rough surface morphology. With the optimum duration of TMAl preflow, crystal quality and surface roughness of GaN can be improved.

Growth and characterization of high quality N-type GaSb/GaAs heterostructure by IMF growth mode using MOCVD for low power application

In this study, we demonstrate the growth of a 150-nm-thick GaSb layer on a GaAs substrate with excellent film quality using the interfacial misfit dislocation growth mode by the Metal–Organic Chemical Vapor Deposition technique. The n-type GaSb epilayer grown on the GaAs substrate has a low threading dislocation density of 3.2 × 106 cm−2 and a surface roughness of approximately 0.8 nm. A high carrier mobility up to 4600 cm2 V−1 s−1 with a carrier concentration of 1.2 × 1017 cm−3 is achieved in this study. The fabricated Al2O3/GaSb/GaAs MOSCAP demonstrated excellent capacitance–voltage (C–V) characteristics with a small frequency dispersion of approximately 2.8%/decade. The results demonstrate the potential of high-mobility Sb-based materials on GaAs for p-type channel CMOS applications in the future.

High V th enhancement mode GaN power devices with high I D, max using hybrid ferroelectric charge trap gate stack

In this work, we demonstrate a new concept for realizing high threshold voltage (V<inf>th</inf>) E-mode GaN power devices with high maximum drain current (I<inf>D, max</inf>). A gate stack ferroelectric blocking film with charge trap layer, achieved a large positive shift of V<inf>th</inf>. The E-mode GaN MIS-HEMTs with high V<inf>th</inf> of 6 V shows I<inf>D, max</inf> 720 mA/mm. The breakdown voltage is above 1100 V.

Buffer-optimized improvement in RF loss of AlGaN/GaN HEMTs on 4-inch silicon (111)

The effect of different buffer layers on the RF losses of GaN-based high-mobility-transistors (HEMTs) on Si substrate has been studied. It is found that the electron inversion layer induced by the residual tensile stress in AlN buffer is responsible for a dominant loss factor. It is first time such mechanisms of the RF loss of GaN/Si is discussed. It is proven that using a thin high-low-high temperature (HLH) AlN buffer reducing the tensile stress in AlN consequently reduces the RF loss.

Growth parameters optimization of GaN high electron mobility transistor structure on silicon carbide substrate

High electron mobility transistors heterostructures of AlGaN/GaN were grown by metalorganic chemical vapor deposition system on silicon carbide substrate. The growth parameters such as AlN buffer thickness, AlN spacer growth time and Al content in AlGaN barrier layer were optimized. Moreover, the effects of chamber pressure and V/III ratio at the initial growth state of GaN on film crystal quality were also investigated. The optimized AlGaN/GaN heterostructure has AlN buffer thickness of 120 nm, AlN spacer growth time of 10 s and Al content of 28% in the barrier layer. Furthermore, as a result of using higher chamber pressure and lower V/III, both the GaN crystal quality and electron mobility in the AlGaN/GaN were also significantly improved. After the growth parameter optimization, the GaN (002) and (102) planes exhibited X-ray rocking curve widths of 209 arcsec and 273 arcsec, respectively. Besides, the AlGaN/GaN structure also has an electron mobility of 1832 cm2/V-s and a sheet electron density of 1.08 ×1013 cm-2, which yielding a sheet resistance of 316 Q/sq.