Recently much attention gained development of “buffer free” AlGaN/GaN HEMT structures with thin high quality AlN nucleation layer for better carrier confinement in the transistor channel mitigating short channel effects and with reduced thermal resistance. In this work results of development of low resistivity Ti/Al/TiN/Au ohmic contacts to such a structures will be presented . The impact of annealing temperature and different metal layer thickness on the ohmic contact formation, morphology and structural and electrical properties was studied. Low contact resistance of 0.28 Ωmm was obtained for metal stack with Ti/Al 20nm/80nm thickness after annealing at 750°C. Developed ohmic contacts were integrated in the AlGaN/GaN HEMT fabrication process. Good electrical characteristics were obtained showing high on-state current up to 0.95 A/mm. These prove applicability of developed process in technology of buffer-free AlGaN/GaN high electron mobility transistors.
In this work we presents effect of ultra high pressure annealing on Si-implanted GaN n-type and p-type epilayers on ammonothermally grown bulk GaN substrates. Samples were blanked implanted with different Si ion fluences from 3x1014 cm-2 to 3x1015 cm-2 and then annealed using UHPA at temperature of 1200, 1300 and 1400°C for 5 minutes at 1 GPa. Ion distribution before and after annealing where investigated using SIMS method showing no Si diffusion in p-type GaN along with Mg diffusion from epilayer and very low Si diffusion in n-type GaN epilayers. X-ray diffraction studies shows that not all defects were recovered after annealing, especially for high ion fluences. Annealing at 1400°C causes changes in implanted GaN morphology. The surface roughness where increased after annealing especially for samples implanted with 3x1015 cm-2Si dose. Our results shows that more work is needed to optimize UHPA parameters for defect recovery in Si-implanted GaN especially for high ion fluences.
Low angle bevelled-mesa structures are crucial for development of high quality GaN p-n high voltage diodes and photodetectors. However, there is lack of details of development of such a process in the literature. Here in this work, we present results of optimization of bevelled mesa fabrication process for vertical GaN p-n diodes using plasma etching through photoresist mask prepared using reflow process. Developed process of formation of low angle bevelled mesa structures was integrated in the vertical GaN p-n diodes on bulk GaN substrates fabrication process. Very low leakage current density below 10-9 A/cm2 and very high Ion/Ioff current ratio over 1013 was obtained. Low values of ideality factor down to 1.5 were obtained as well. These prove applicability of developed process in technology of vertical GaN p-n diodes on bulk gallium nitride substrates.
Normally-off AlGaN/GaN HEMTs with p-GaN-gate, which offer high drain current and low on-state resistance at high threshold voltage and breakdown voltage values above 600V, are particularly attractive for high-power electronics applications. In this work we present the results of development of high power normally-off p-GaN gate AlGaN/GaN high electron mobility transistors carried out at Łukasiewicz Research Network-Institute of Microelectronics and Photonics. We have developed key technological steps i.e. selective etching of p-GaN layers over AlGaN, deposition of proper passivation layer as well as thermally stable isolation of adjacent devices using selective Fe+ ion implantation, which were integrated in the process flow of manufacturing of high power transistors. Finally we have shown measurements of developed normally-off p-GaN gate AlGaN/GaN HEMT power transistors assembled using in-house developed process in TO-220 package.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.