RESEARCH ARTICLE
Luminescence properties of blue and green dual wavelength
InGaN/GaN multi-quantum well light-emitting diode
Feng WEN, Lirong HUANG (✉), Liangzhu TONG, Dexiu HUANG, Deming LIU
Wuhan National Laboratory for Optoelectronics, College of Optoelectronic Science and Engineering, Huazhong University of Science and
Technology, Wuhan 430074, China
© Higher Education Press and Springer-Verlag 2009
Abstract Blue and green dual wavelength InGaN/GaN
multi-quantum well (MQW) light-emitting diode (LED)
has wide applications in full color display, monolithic
white LED and solid state lighting, etc. Blue and green
dual wavelength LEDs, which consist of InGaN strain-
reduction layer, green InGaN/GaN MQW and blue InGaN/
GaN MQW, were grown by metal-organic chemical vapor
deposition (MOCVD), and the luminescence properties of
dual wavelength LEDs with different well arrangements
were studied by photoluminescence and electrolumines-
cence. The experimental results indicated that well position
played an important role on the luminescence evolvement
from photoluminescence to electroluminescence.
Keywords multi-quantum well (MQW), luminescence,
dual-wavelength, metal-organic chemical vapor deposition
(MOCVD)
1 Introduction
GaN based materials cover a wide bandgap from 0.6 eV
(InN) to 6.2 eV (AlN) and are capable of emitting light
with wavelength ranging from ultraviolet to visible and
even to infrared. With the technological breakthrough in
material epitaxy and chip fabrication process, GaN-based
blue light-emitting diode (LED), green LED and near
ultraviolet LED have been commercially available and
extensively used. Compared with single color LEDs,
multi-wavelength GaN based LEDs have progressed
slowly, in spite of their importance in full color display,
monolithic white light-emitting diode and solid state
lighting, etc. [1–4]. For example, blue and green dual
wavelength LED can provide blue light and green light,
which are two of the three primary colors. Also, the color
tunablity make dual wavelength LED a good candidate in
full-color display.
In this paper, we grew blue and green dual wavelength
LEDs by metal-organic chemical vapor deposition
(MOCVD), the luminescence properties of dual wave-
length LEDs with different well arrangements were
analyzed by photoluminescence (PL) and electrolumines-
cence (EL).
2 Experiments
The samples were grown on c-plane sapphire substrate by
Thomas Swan close-coupled-showerhead low-pressure
MOCVD system. Trimethylindium (TMIn), trimethylgal-
lium (TMGa), trimethylaluminium (TMAl) and NH
3
were
used as In, Ga, Al, N precursors, respectively. H
2
and N
2
were used as the carrier gas. SiH
4
and biscyclopentadienyl
magnesium (CP
2
Mg) were used as N-type and P-type
doping sources, respectively.
The epitaxial growth of green LED is difficult, because
high Indium (In) content InGaN is difficult to grow due to
the large strain between InGaN and GaN [5], and the low
miscibility of InN in GaN [6]. Therefore, we introduced a
low In content InGaN layer to serve as strain reduction
layer [7], thus enhancing In incorporation in the following-
grown green InGaN multi-quantum well (MQW) and
extending its emission wavelength to a longer wavelength.
We grew four kinds of samples. The schematic
structures of sample A and sample B are shown in
Figs. 1(a) and 1(b), respectively, and the structure of
sample C and sample D are shown in Figs. 2(a) and 2(b),
respectively. Sample A is green InGaN/GaN MQW, which
consists of 25 nm-thick GaN nucleation layer grown at
525°C, followed by undoped GaN buffer layer grown at
1050°C, then 5 periods of In
0.15
Ga
0.85
N (3 nm)/GaN
(14 nm) MQWs as active region; the growing temperature
Received August 20, 2009; accepted September 23, 2009
E-mail: hlr5649@163.com
Front. Optoelectron. China 2009, 2(4): 446–449
DOI 10.1007/s12200-009-0070-4