Electroluminescence Properties of InGaN/AlGaN/GaN Light Emitting Diodes with Quantum Wells
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A.N.Kovalev, F.I.Manyakhin. Moscow Institute of Steel and Alloys,
Moscow, Russia. E-mail:yunovich @scon 175.phys.msu. su
Cite this article as : MRS Internet J. Nitride Semicond. Res. 4S1, G6.29 (1999)
Abstract Electroluminescence
spectra
of
light-emitting
diodes
based
on
InGaN/AIGaN/GaN heterostructures with single and multiple quantum wells (QWs) are analyzed by models of radiative recombination in 2D-structures with band tails. Equations of the model fit spectra quite good in a wide range of currents. Parameters of the fit are discussed and compared for single and multiple QWs. Tunnel effects play a sufficient role in blue LEDs with single QWs at low currents; they can be neglected in LEDs with multiple QWs. A new spectral band was detected at the high energy side of the spectra of green LEDs with multiple QWs; it is attributed with large scale inhomogenities of In distribution in InGaN QWs.*) *) This work proceeds previous results of our group presented on EGW-3 [I].
Introduction The problems of recombination mechanisms in InGaN/AIGaN/GaN heterostructures are not fully understood in spite of great progress in the development of GaN-based light-emitting diodes (LEDs). We have studied luminescence spectra of two groups of LED's based on structures with single InGaN quantum wells (SQWs, sent to Moscow University by Dr. S.Nakamura, Nichia Chemical Co.) and multiple quantum wells (MQWs, sent to Moscow University by Dr. M.Koike, Toyoda Gosei Co.) in a wide range of currents [2-6]. A model of radiative recombination in 2D-structures with band tails caused by potential fluctuations was successfully applied to describe the spectra [2-4]; tunnel radiative recombination was detected at G 6.29 Mat. Res. Soc. Symp. Proc. Vol. 537 © 1999 Materials Research Society
low currents [5]. In this work spectra of blue and green LEDs with SQW and MQW active layers are compared and the model of recombination is analyzed. Changes of the parameters with current J and voltage V are discussed. Fitting: Fit main band: 10mA O0.mA
2.71 eV ( ;• -':'
"
-
2. M4.....
5..5.... ......0.5 -- o.11mr 0.3 ..............
0,1
0.06 r
0,01 8
2.1
IE-3
eV.............
U
-V-73
IE-4 •I~ exp (-hadE, )'•
. I,6
1.8
.
~E
.
2.0
E=55 meV.
2.6
2,2 2,4 energy, eV
2.8
•-
I,. 8
2,67 eV •
"
2,3
2.4
2.5 2,6
2.7
2,37
10pA , 1 !A
A
10 I 0.1
I x hoEE phv a~e o
S.......
S...........
ImA •.
,,./
0pA ........... 20pA
IE-4 IE-6
BffkAN 0• 0.1MkA : .........
1.6
I.e
S-0o.6 mi •.-..-.- .. 2o.1m
S.....
C 0.01
nkA. o.5e
S--
2,9
E~xpenmetal so1A 5 1- exp(- h./E,) - 20mA l, 64 mneV- -10.A 5.mA ...........
IE-3 --..
2.8
Figure 2a. Electroluminescence spectra
I ~exp(-holt 42 me .kT E
0.160pA%,
90.5A
2.2
energy,eV
B20 037 O0.1 1.t1mA A ..... B10mA a
I
1.9 2,0 2.1
of green LED with SQW.
) I- exp( hlE 6 t 10mA E~.54 meV -~ Bxe50MA Filling: roooerknerft:
0
2.407 OV
3,0
of blue LED with SQW.
Oan ....... 81.... lA
S............ 0O.022
............ 40.p
Figure la. Electroluminescence spectra
10
0.5MA ......
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