Browsing by Author "Lumbantoruan, Franky"

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Analysis of Leakage Current Mechanism for Ni/Au Schottky Contact on InAlGaN/GaN HEMT
(2018-06-06)
Lumbantoruan, Franky
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Wu, Chia-Hsun
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Zheng, Xia-Xi
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Singh, Sankalp K.
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Dee, Chang-Fu
The gate leakage mechanism for InAlGaN/GaN high electron mobility transistors (HEMTs) is systematically studied using temperature-dependent gate current-voltage characteristics. The electric field across the barrier layer is calculated through the extracted polarization charge and dielectric constant of the InAlGaN/GaN HEMT. The gate current of the InAlGaN/GaN HEMT is analyzed by fitting the experimental data using Themionic Emission (TE), Poole-Frenkel (PF), and Fowler-Nordheim (FN) tunneling. The results show that 1) reverse leakage current in the thin InAlGaN barrier layer is dominated by FN tunneling due to triangular barrier formation; 2) for thicker barrier layer, the reverse leakage current at low electric field (<2.23MVcm(-1)) is dominated by PF emission; 3) at high electric field near the threshold voltage the FN tunneling dominates. Extraction of effective barrier height by fitting the experimental data with models leads to the suggestion for the improvement of the device leakage current.
BUFFER-OPTIMIZED IMPROVEMENT IN RF LOSS OF ALGAN/GAN HEMTS ON 4-INCH SILICON (111)
(2017-01-01)
Luong, Tien Tung
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Lumbantoruan, Franky
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Chen, Yen-Yu
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Ho, Yen-Teng
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Lin, Yueh-Chin
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.
Investigation of TMAl preflow to the properties of AlN and GaN film grown on Si(111) by MOCVD
(2014-01-01)
Lumbantoruan, Franky
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Wong, Yuan-Yee
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Wu, Yue-Han
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Huang, Wei-Ching
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Shrestra, Niraj Man
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.
RF loss mechanisms in GaN-based high-electron-mobility-transistor on silicon: Role of an inversion channel at the AlN/Si interface
(2017-07-01)
Luong, Tien Tung
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Lumbantoruan, Franky
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Chen, Yen-Yu
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Ho, Yen-Teng
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Weng, You-Chen
One of the epitaxial issues pertaining to the growth of AlGaN/GaN HEMTs on Si is the decrease of parasitic losses that can adversely impact the RF device performances. We characterized the microwave losses in coplanar waveguides (CPWs) on GaN-based high-electron-mobility-transistors (HEMTs) and their buffer layers on Silicon substrate, up to 40GHz. The RF losses depend not only on the crystalline quality but also on the residual tensile stress in AlN buffer, as well as its thickness. The mechanism of interfacial lossy channel induced by the piezoelectric field is discussed. Adopting a thin high-low-high temperature (HLH) AlN buffer can help to reduce the tensile stress leading to a reduction of RF losses. We suggest that a thinner p-type AlN and/or p-AlGaN-on-thin AlN near the interface can suppress the electron interfacial lossy channel, which helps the GaN-HEMT-on-HR Si to remain in a high frequency range and at high-temperature operation. (C) 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
Structural and electrical properties analysis of InAlGaN/GaN heterostructures grown at elevated temperatures by MOCVD
(2018-11-01)
Lumbantoruan, Franky
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Zheng, Xia-Xi
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Huang, Jian-Hao
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Huang, Ren-Yao
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Mangasa, Firman
We report the effects of the growth temperature on the structural and electrical properties of the InAlGaN/GaN heterostructures grown on c-plane sapphire substrates. X-ray Photoelectron Spectroscopy and Atomic Force Microscopy measurements results indicate that the InAlGaN layer properties is strongly dependent on the growth temperature. It is observed that the Gallium incorporation increases with the increase of the growth temperature. Meanwhile, the surface roughness decreases from 0.49 nm to 0.34 nm with the increase of growth temperature. The variation of structural properties, composition and surface morphology influences the transport properties of the InAlGaN/GaN heterostructures. High 2DEG electron density, low sheet resistance and good C-V response with a steep slope for InAlGaN/GaN HEMT were achieved at an optimized growth temperature window between 900 degrees C and 950 degrees C.