AVS 49th International Symposium
    Electronic Materials and Devices Monday Sessions
       Session EL+SC+MI-MoM

Paper EL+SC+MI-MoM9
N-type Diamond Electronics With Nitrogen Doped Ultrananocrystalline Diamond

Monday, November 4, 2002, 11:00 am, Room C-107

Session: Semiconductors
Presenter: J.E. Gerbi, Argonne National Laboratory
Authors: J.E. Gerbi, Argonne National Laboratory
B.W. Alphenaar, University of Louisville
O. Auciello, Argonne National Laboratory
J. Birrell, University of Illinois at Urbana-Champaign
J.A. Carlisle, Argonne National Laboratory
D.M. Gruen, Argonne National Laboratory
Correspondent: Click to Email
Thin diamond films have extremely attractive properties for electronic device applications: high thermal conductivity, carrier mobility, and breakdown fields. However, efforts to create diamond based electronic devices have been hampered by the difficulty in incorporating dopants. Attempts to dope diamond films have resulted in low p-type carrier concentrations or unstable p-type surface layers. N-type doping has been even less successful, and it has not yet been possible to synthesize n-type diamond films with sufficiently high room-temperature conductivities. Ultra-nanocrystalline diamond (UNCD) is a fine-grained (3-5nm), phase-pure diamond material with atomically abrupt grain boundaries. Synthesized by microwave CVD using Ar-rich Ar/CH@sub 4@ plasmas, both the structure and electronic properties of UNCD can be tailored by doping with a controlled amount of N@sub 2@ in the plasma. As the N@sub 2@ content in the plasma increases to 20% , the grain size and grain boundary width of the UNCD films increase. This microstructural change correlates with a striking increase in room-temperature conductivity . Most importantly, nitrogen doped UNCD films are n-type with activation energies as low as 0.05 eV. This is striking, as traditional nitrogen substitutional doping of diamond produces a very deep state of 1.7eV, rendering the material useless for room-temperature applications. We use this material to demonstrate the first n-type diamond MESFET that can be operated at room temperature. We have characterized the films using Raman spectroscopy, NEXAFS, SIMS, Hall mobility measurements, and HRTEM, and measure device properties such as I-V curves and transconductance. The ohmic vs. Schottky behavior of various contacts to nitrogen doped UNCD as a function of growth chemistry has also been studied. A discussion of the microstructure-property relationship of nitrogen-doped UNCD films will be presented in the context of the UNCD-based MESFET performance.