Two different features of ZnO: Transparent ZnO:Ga electrodes for InGaN-LEDs and homoepitaxial ZnO films for UV-LEDs

K. Nakahara, H. Yuji, K. Tamura, S. Akasaka, H. Tampo, S. Niki, Atsushi Tsukazaki, A. Ohtomo, M. Kawasaki

Research output: Chapter in Book/Report/Conference proceedingConference contribution

11 Citations (Scopus)


We have used molecular beam epitaxy (MBE) to deposit gallium (Ga) doped ZnO (ZnO:Ga) films. The as-deposited ZnO:Ga films have worked as ohmic contacts for the p-type GaN layers without any kinds of post annealing process. The as-deposited ZnO:Ga films on a-plane sapphire substrates have resistivities of 2-4×10-4 Ωcm, and over 80 % transparency in the near-UV and visible wavelength regions. The brightness of InGaN light-emitting diodes (LEDs) with ZnO:Ga p-contacts has doubled compared to LEDs with conventional Ni/Au semi-transparent p-contacts when measuring the brightness from right above the device surfaces. In addition, using MBE, we have grown homoepitaxial polar ZnO films on (000+1)-plane (+c-plane) ZnO substrates, and also grown non-polar ZnO films on (1-100)-plane (m-plane) and (11-20)-plane (a-plane) ZnO substrates. Growth temperatures have not affected nitrogen-doping levels for +c-axis oriented (Zn-polar) nitrogen doped ZnO (ZnO:N) films. The phenomena were quite different from that for (000-1)-axis (-c-axis) oriented (oxygen-polar) growth, where nitrogen concentrations in ZnO decrease with increasing growth temperatures. We have observed c-axis direction growth for both of m-axis and a-axis oriented films. Oxygen-rich growth conditions flatten surfaces for both m-axis and a-axis oriented films, and the surfaces of m-axis oriented ZnO films flatten with increasing growth temperatures. Nitrogen concentrations in m-axis oriented ZnO:N films have been independent on growth temperatures.

Original languageEnglish
Title of host publicationZinc Oxide Materials and Devices
Publication statusPublished - 2006 May 25
EventZinc Oxide Materials and Devices - San Jose, CA, United States
Duration: 2006 Jan 222006 Jan 25

Publication series

NameProceedings of SPIE - The International Society for Optical Engineering
ISSN (Print)0277-786X


OtherZinc Oxide Materials and Devices
Country/TerritoryUnited States
CitySan Jose, CA

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Condensed Matter Physics
  • Computer Science Applications
  • Applied Mathematics
  • Electrical and Electronic Engineering


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