Formation of two-dimensional electron gas and enhancement of electron mobility by Zn polar ZnMgO/ZnO heterostructures

H. Tampo, H. Shibata, K. Matsubara, A. Yamada, P. Fons, M. Yamagata, H. Kanie, S. Niki

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


A two-dimensional electron gas (2DEG) was observed in Zn polar ZnMgO/ZnO (ZnMgO on ZnO) heterostructures grown by radical source molecular beam epitaxy. Reflection high energy electron diffraction patterns taken during the growth of the ZnMgO layer remained streaky; x-ray diffraction measurements showed no evidence of phase separation for up 44 % Mg composition. These results shows that the high quality ZnMgO layers up to 44 % Mg composition were obtained without phase separation. The electron mobility of the ZnMgO/ZnO heterostructures dramatically increased with increasing Mg composition and the electron mobility (μ∼250 cm2/Vs) at RT reached a value more than twice that of an undoped ZnO layer (μ∼100 cm2/Vs) due to the 2DEG formation. The carrier concentration in turn reached values as high as ∼1×1013 cm-2 and remained nearly constant regardless of Mg composition. Strong confinement of electrons at the ZnMgO/ZnO interface was confirmed by C-V measurements with a concentration of over 4×1019 cm-3. Temperature-dependent Hall measurements of ZnMgO/ZnO heterostructures also exhibited properties associated with well defined heterostructures. The Hall mobility increased monotonically with decreasing temperature, reaching a value of 2750 cm2/Vs at 4 K. Zn polar "ZnMgO on ZnO" structures are easy to adapt to a top-gate device. These results open new possibilities for high electron mobility transistors (HEMTs) based upon ZnO based materials.

Original languageEnglish
Title of host publicationZinc Oxide Materials and Devices II
Publication statusPublished - 2007
Externally publishedYes
EventZinc Oxide Materials and Devices II - San Jose, CA, United States
Duration: 2007 Jan 212007 Jan 24

Publication series

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


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


  • HEMT
  • Heterostructure
  • Polarity
  • Two-dimensional electron gas (2DEG)
  • ZnMgO
  • ZnO

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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