AVS 51st International Symposium
    Semiconductors Thursday Sessions
       Session SC+EM-ThM

Paper SC+EM-ThM6
Conductive Atomic Force Microscopy Studies of Forward and Reverse Current Conduction in GaN Films

Thursday, November 18, 2004, 10:00 am, Room 304B

Session: Wide Bandgap Semiconductors
Presenter: A.A. Baski, Virginia Commonwealth University
Authors: A.A. Baski, Virginia Commonwealth University
J. Spradlin, Virginia Commonwealth University
S. Dogan, Virginia Commonwealth University
H. Morkoc, Virginia Commonwealth University
Correspondent: Click to Email
We have investigated the current conduction of homo- and heteroepitaxial GaN-based films using conductive atomic force microscopy (C-AFM). For the case of a homoepitaxial film grown by MBE on HVPE template, C-AFM shows premature current breakdown at the centers of hillocks associated with screw dislocations, consistent with the results of other groups. Local C-AFM current-voltage curves of such dislocations indicate a Frenkel-Poole mechanism for forward conduction on defective regions, as opposed to field emission on non-defective regions. In the case of heteroepitaxial GaN films grown on sapphire, C-AFM data do not show a straightforward correlation between topography and current conduction. We observe, however, that films with more rectifying Schottky behavior via standard I-V measurements produce forward and reverse bias C-AFM images with strong asymmetry. In addition, standard I-V data indicate a field emission (forward bias) or hopping (reverse bias) mechanism for a high quality rectifying film, and a Frenkel-Poole mechanism for a lower quality film. This behavior is consistent with the C-AFM I-V data of defective regions on the homoepitaxial film, which also show Frenkel-Poole conduction in forward bias.