Abstract
A normally-off GaN double-implanted vertical MOSFET (DMOSFET) with an atomic layer deposition (ALD)-Al2O3 gate dielectric film on a free-standing GaN substrate fabricated by triple ion implantation is presented. The DMOSFET was formed with Si ion implanted source regions in a Mg ion implanted p-type base with N ion implanted termination regions. A maximum drain current of 115 mA/mm, maximum transconductance of 19 mS/mm at a drain voltage of 15 V, and a threshold voltage of 3.6 V were obtained for the fabricated DMOSFET with a gate length of 0.4 μm with an estimated p-type base Mg surface concentration of 5 × 1018 cm−3. The difference between calculated and measured Vths could be due to the activation ratio of ion-implanted Mg as well as Fermi level pinning and the interface state density. On-resistance of 9.3 mΩ·cm2 estimated from the linear region was also attained. Blocking voltage at off-state was 213 V. The fully ion implanted GaN DMOSFET is a promising candidate for future high-voltage and high-power applications.
Highlights
Wide-bandgap-based vertical power devices with normally-off operation have been developed in recent years [1,2,3,4,5,6,7,8]
Many defects were still present in the Si implanted layer after high-temperature but it seems that the defects thatdue were to more clearly seen after clearly seen after annealing in the Mgannealing, ion implanted layer were the localization of Mg atoms
Lower Ron could be achieved by reducing the sheet resistivity of the n-type epitaxial layer and pulsed Ids -Vds characteristics of the fabricated Gallium nitride (GaN) double-implanted vertical MOSFET (DMOSFET) measured at pulse width/period of the cell pitch of the DMOSFET
Summary
Wide-bandgap-based vertical power devices with normally-off operation have been developed in recent years [1,2,3,4,5,6,7,8]. The early SiC power MOSFETs were vertical trench MOSFETs (UMOSFETs), in which the base and source regions were formed epitaxially, without the need for ion implantation [2]. Recent GaN vertical power transistors have trench gate structures and low-resistance source regions utilized two-dimensional electron gas (2DEG) produced by polarization charges at the hetero-interface [19]. Ion implantation is a widely used doping technology for Si and SiC MOSFETs but it has been difficult to form a p-type doping layer using ion implantation technology for GaN device fabrication process until recently. Ion implantation is a widely used doping technology for Si and SiC MOSFETs but it has been difficult to form a p-type doping using ion implantation technology for GaN device fabrication process
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