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Screw Dislocations in GaN Grown by Different Methods

Published online by Cambridge University Press:  22 January 2004

Z. Liliental-Weber ,
D. Zakharov ,
J. Jasinski ,
M.A. O'Keefe  and
H. Morkoc
Z. Liliental-Weber
Affiliation:
Lawrence Berkeley National Laboratory, m/s 62R0203-8255, Berkeley, CA 94720, USA
D. Zakharov
Affiliation:
Lawrence Berkeley National Laboratory, m/s 62R0203-8255, Berkeley, CA 94720, USA
J. Jasinski
Affiliation:
Lawrence Berkeley National Laboratory, m/s 62R0203-8255, Berkeley, CA 94720, USA
M.A. O'Keefe
Affiliation:
Lawrence Berkeley National Laboratory, m/s 62R0203-8255, Berkeley, CA 94720, USA
H. Morkoc
Affiliation:
Virginia Commonwealth University, Richmond, VA 23284, USA
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Abstract

A study of screw dislocations in hydride-vapor-phase-epitaxy (HVPE) template and molecular-beam-epitaxy (MBE) overlayers was performed using transmission electron microscopy (TEM) in plan view and in cross section. It was observed that screw dislocations in the HVPE layers were decorated by small voids arranged along the screw axis. However, no voids were observed along screw dislocations in MBE overlayers. This was true both for MBE samples grown under Ga-lean and Ga-rich conditions. Dislocation core structures have been studied in these samples in the plan-view configuration. These experiments were supported by image simulation using the most recent models. A direct reconstruction of the phase and amplitude of the scattered electron wave from a focal series of high-resolution images was applied. It was shown that the core structures of screw dislocations in the studied materials were filled. The filed dislocation cores in an MBE samples were stoichiometric. However, in HVPE materials, single atomic columns show substantial differences in intensities and might indicate the possibility of higher Ga concentration in the core than in the matrix. A much lower intensity of the atomic column at the tip of the void was observed. This might suggest presence of lighter elements, such as oxygen, responsible for their formation.

Keywords

core of screw dislocationpinholeselectron exit-wave reconstructionGaN grown by HVPE and MBE
Type
Research Article
Information
Microscopy and Microanalysis , Volume 10 , Issue 1 , February 2004 , pp. 47 - 54
Copyright
© 2004 Microscopy Society of America

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References

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