Mg Segregation, Difficulties of P-Doping in GaN
This article was presented as part of Symposium W, "Gallium Nitride and Related Alloys" at the 1999 Fall Meeting of the Materials Research Society held in Boston, Massachusetts, November 28-December 3
Abstract
Transmission electron microscopy has been used to study defects formed in Mg-doped
GaN crystals. Three types of crystals have been studied: bulk crystals grown by a high
pressure and high temperature process with Mg added to the Ga solution and two types of
crystals grown by metal-organic chemical vapor deposition (MOCVD) where Mg was
either delta-doped or continuously doped. Spontaneous ordering was observed in bulk
crystals. The ordering consists of Mg rich planar defects on basal planes separated by
10.4 nm and occurs only for growth in the N to Ga polar direction (000
N polarity).
These planar defects exhibit the characteristics of stacking faults with a shift vector of a
1/3 [100] +c/2 but some other features identify these defects as inversion domains.
Different type of defects were formed on the opposite site of the crystal (Ga to N polar
direction), where the growth rate is also an order of magnitude faster compared to the
growth with N-polarity. These defects are three-dimensional: pyramidal and rectangular,
empty inside with Mg segregation on internal surfaces. The same types of defects seen
for the two growth polarities in the bulk crystals were also observed in the MOCVD
grown GaN samples with Mg delta doping, but were not observed in the crystals where
Mg was added continuously.
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Cite this article as: MRS Internet J. Nitride Semicond. Res. 5S1, W9.7 (2000).
last updated Wednesday, May 17, 2000 4:57:18 PM.
© 2000 The Materials Research Society