Analysis of the Visible and UV Electroluminescence in Homojunction GaN LED's
F. Calle, E. Monroy, F. J. Sánchez, E. Muñoz
Dpt. Ingeniería Electrónica, E.T.S.I. Telecomunicación, Politécnica, Ciudad Universitaria
B. Beaumont, S. Haffouz, M. Leroux, Pierre Gibart
Centre de Recherche sur l'Hétéroépitaxie et ses Applications, CRHEA-CNRS
This article was received on Friday, June 19, 1998 and
accepted on Wednesday, September 16, 1998. Abstract
The electrical and electroluminescent properties of MOVPE GaN p-n
homojunctions have been analyzed as a function of temperature and bias.
Electroluminescence is observed for V>3 V under dc and ac conditions. The
main emission at low T is a donor-acceptor transition involving shallow
acceptors, though it disappears at higher T due to the ionization of the
acceptors and compensation by ionized donors. Room temperature dc and ac
electroluminescence spectra evolve under increasing bias from a blue-shifting
visible band involving deep states at the p-type side of the p-n junction, to a
band-to-band UV recombination at high bias. In agreement, the superlinear
dependence of light-current characteristics at low current injection becomes
linear when the defects are saturated. Time analysis of the spectra vs pulse
duration and duty cycle allows the determination of the visible radiative
recombination and relaxation times associated to the Mg-related deep states,
which are found to behave as acceptors lying 0.55 eV above the valence band. A
simple 3-level model is able to explain the visible emission, which involves
the conduction band (or shallow donor) and those deep acceptors in the p-layer.
Optimum UV/visible ratio emission requires intense and relatively long pulses,
with a high duty cycle to impede visible recombination.Outline
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Cite this article as: MRS Internet J. Nitride Semicond. Res. 3, 24(1998).
last updated Wednesday, September 16, 1998 11:17:28 PM.© 1998 The Materials Research Society
