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Title: Adjustment of threshold voltage in AlN/AlGaN/GaN high-electron mobility transistors by plasma oxidation and Al{sub 2}O{sub 3} atomic layer deposition overgrowth

We discuss possibilities of adjustment of a threshold voltage V{sub T} in normally off GaN high-electron mobility transistors (HEMTs) without compromising a maximal drain current I{sub DSmax}. Techniques of a low power plasma or thermal oxidation of 2-nm thick AlN cap over 3-nm thick AlGaN barrier are developed and calibrated for a thorough oxidation of the cap with a minimal density of surface donors at the inherent oxide-semiconductor interface. It has been shown that while a thermal oxidation technique leads to the channel and/or interface degradation, low density of surface donors and scalability of V{sub T} with additionally overgrown Al{sub 2}O{sub 3} may be obtained for plasma oxidized HEMTs. With 10-nm thick Al{sub 2}O{sub 3} deposited at 100 °C by atomic-layer deposition, we obtained V{sub T} of 1.6 V and I{sub DSmax} of 0.48 A/mm at a gate voltage of V{sub GS} = 8 V. Density of surface donors was estimated to be about 1.2 × 10{sup 13} cm{sup −2}, leaving most of the negative polarization charge at the semiconductor surface uncompensated. Further reduction of surface donors may be needed for even higher V{sub T}.
Authors:
; ; ; ; ; ; ; ;  [1] ; ;  [2] ; ;  [3]
  1. Institute of Electrical Engineering SAS, Dúbravska cesta 9, 841 04 Bratislava (Slovakia)
  2. Faculty of Electrical Engineering and Information Technology, STU Bratislava, Ilkovičova 3, 812 19 Bratislava (Slovakia)
  3. EpiGaN NV, Kempische steenweg 293, 3500 Hasselt (Belgium)
Publication Date:
OSTI Identifier:
22257125
Resource Type:
Journal Article
Resource Relation:
Journal Name: Applied Physics Letters; Journal Volume: 104; Journal Issue: 1; Other Information: (c) 2014 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; ALUMINIUM NITRIDES; ALUMINIUM OXIDES; ELECTRIC POTENTIAL; ELECTRON MOBILITY; GALLIUM NITRIDES; OXIDATION; SEMICONDUCTOR MATERIALS; SURFACES; TRANSISTORS