Accession Number : ADA630604


Title :   Dopant-Free GaN/AlN/AlGaN Radial Nanowire Heterostructures as High Electron Mobility Transistors


Descriptive Note : Journal article


Corporate Author : HARVARD UNIV CAMBRIDGE MA DEPT OF CHEMISTRY AND CHEMICAL BIOLOGY


Personal Author(s) : Li, Yat ; Xiang, Jie ; Qian, Fang ; Gradecak, Silvija ; Wu, Yue ; Yan, Hao ; Blom, Douglas A ; Lieber, Charles M


Full Text : https://apps.dtic.mil/dtic/tr/fulltext/u2/a630604.pdf


Report Date : 10 Jun 2006


Pagination or Media Count : 8


Abstract : We report the rational synthesis of dopant-free GaN/AlN/AlGaN radial nanowire heterostructures and their implementation as high electron mobility transistors (HEMTs). The radial nanowire heterostructures were prepared by sequential shell growth immediately following nanowire elongation using metal-organic chemical vapor deposition (MOCVD). Transmission electron microscopy (TEM) studies reveal that the GaN/ AlN/AlGaN radial nanowire heterostructures are dislocation-free single crystals. In addition, the thicknesses and compositions of the individual AlN and AlGaN shells were unambiguously identified using cross-sectional high-angle annular darkfield scanning transmission electron microscopy (HAADF-STEM). Transport measurements carried out on GaN/AlN/AlGaN and GaN nanowires prepared using similar conditions demonstrate the existence of electron gas in the undoped GaN/AlN/AlGaN nanowire heterostructures and also yield an intrinsic electron mobility of 3100 cm2/Vs and 21 000 cm2/Vs at room temperature and 5 K, respectively, for the heterostructure. Field-effect transistors fabricated with ZrO2 dielectrics and metal top gates showed excellent gate coupling with near ideal subthreshold slopes of 68 mV/dec, an on/off current ratio of 107, and scaled on-current and transconductance values of 500 mA/mm and 420 mS/mm. The ability to control synthetically the electronic properties of nanowires using band structure design in III-nitride radial nanowire heterostructures opens up new opportunities for nanoelectronics and provides a new platform to study the physics of low-dimensional electron gases.


Descriptors :   *GALLIUM NITRIDES , *HIGH ELECTRON MOBILITY TRANSISTORS , *NANOWIRES , CHEMICAL VAPOR DEPOSITION , CROSS SECTIONS , ELECTRON GAS , ELONGATION , FIELD EFFECT TRANSISTORS , REPRINTS , ROOM TEMPERATURE , SINGLE CRYSTALS , TRANSMISSION ELECTRON MICROSCOPY


Subject Categories : Electrical and Electronic Equipment


Distribution Statement : APPROVED FOR PUBLIC RELEASE