p-doping of GaN by MOVPE
S. Haffouz, B. Beaumont, M. Leroux, M. Laugt, P. Lorenzini, Pierre GIBART
Centre de Recherche sur l'Hétéroépitaxie et ses Applications, CRHEA-CNRS
L.G.Hubert-Pfalzgraf
Laboratoire de Chimie Moléculaire,Faculté des Sciences, Nice, France
This article was received on Wednesday, July 2, 1997 and
accepted on Tuesday, September 16, 1997. Abstract
Mg has been widely used as p-doping species despite its intrinsic
difficulties. It is nowadays well established that during the growth process of
Mg doped GaN, atomic H is generated from the decomposition of NH3
and Mg-H complexes are formed in the layer. This has been for instance shown by
the occurrence of LO mode in IR absorption, and by the observation of the Mg-H
local vibration modes. This H passivation limits the electrical activity of Mg,
therefore an activation process is required to get full activation of the Mg
atoms. In the present study, bismethylcyclopentadienyl magnesium
[(MeCp)2Mg] was used as precursor. However, this precursor reacts in
the gas phase with NH3 to produce tiny solid particles as evidenced
by a very bright diffuse emission visible along the laser beam used for
reflectometry measurements. This simplest obvious product would be
[(MeCp)Mg(NH2)]m (m
2). To limit this drawback, Ga and
Mg precursor lines have been separated. With proper in situ heat treatment,
doping densities up to 1.5x1018 cm-3 have been obtained. PL spectra of
lightly Mg doped samples (1016 cm-3) are dominated by shallow
donor-acceptor pairs whereas for higher doping densities ( 1018
cm-3), the luminescence is dominated by a broad band in the 2.7-2.9
eV range. GaN LEDs were fabricated from Si doped (n-type) and Mg-doped (p-type)
GaN, these LEDs emit in the blue-UV range.Outline
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Cite this article as: MRS Internet J. Nitride Semicond. Res. 2, 37(1997).
last updated Thursday, November 2, 2000 5:40:40 PM.© 1997-2000 The Materials Research Society
