| About this Abstract |
| Meeting |
2011 Electronic Materials Conference
|
| Symposium
|
2011 Electronic Materials Conference
|
| Presentation Title |
W8, Schottky Barrier Height and Interface Chemistry for Metals Contacted to Low Dislocation Density AlGaN Grown on C-Oriented AlN Wafers |
| Author(s) |
James Tweedie, Anthony Rice, Ramon Collazo, Seiji Mita, Jinqiao Xie, Zlatko Sitar |
| On-Site Speaker (Planned) |
James Tweedie |
| Abstract Scope |
Devices based on III-nitrides and their alloys have attracted interest for high temperature and high power applications. In this paper we investigate the Schottky barrier heights and interface chemistry for a collection of representative unannealed metals (Au, Ni, Al, Ti) on high Al mole fraction AlGaN films. Metal work functions range from 4.3 to 5.1 eV. The low dislocation density 300 nm Si doped n-type AlGaN films were grown on bulk c-oriented AlN single crystal wafers by low pressure metal organic chemical vapor deposition (MOCVD) in a reactor with a shower-head configuration. Samples were mounted on a Mo puck and top contacted with In to a metal clip to establish an electrical ground through the sample holder. The mounted samples were then transferred ex situ directly to an ultra high vacuum (UHV) system where the surfaces were studied using x-ray photoelectron spectroscopy (XPS). The samples were transferred within the UHV system to an electron beam evaporation chamber where the contact metals were deposited. The samples were then returned to the XPS chamber for further characterization. Using a method developed by Waldrop and Grant, Schottky barrier heights were measured directly by measuring shifts relative to the valence band maximum (VBM) of reference photoelectron lines corresponding to the AlGaN film at the interface after metal deposition. A series of thicknesses (1 - 15 nm) for each of the contact metals was used to monitor the evolution of the Schottky barrier height. For Au contacts thicker than 6 nm back bending was observed, while for the other metals the reference photoelectron line was extinguished before significant back bending was observed. The Schottky barriers measured by XPS were compared with barriers derived from I-V measurements and were shown to be in good agreement. Samples were characterized ex situ by high resolution x-ray diffraction (HRXRD) to determine the AlGaN composition and strain state. Fitting the Schottky Barrier height as a function of the work function of the metal, the electron affinity of Al(0.75)Ga(0.25)N was shown to be approximately 3 eV. Furthermore, the Schottky Mott model holds for the metal-AlGaN interfaces when surface oxidation is limited. |
| Proceedings Inclusion? |
Undecided |