Third Day Poster Session, 17 June 2010 - NanoTR-VI

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Poster Session, Thursday, June 17
Theme F686 - N1123
Characterization of a Multilayer GaAs/AlGaAs Broadband Quantum Well Infrared Photodetectors
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UHülya KuruUP P*, Burcu ArpapayP P, Bülent ArkanP P, Bülent AslanP Uur SerincanP
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PDepartment of Physics, Anadolu University, Eskiehir 26470, Turkey
Abstract-In this study, we report on the investigation of a multilayer GaAs/AlGaAs quantum well infrared photodetector designed for 8-12 m
spectral range detection. Fabricated devices were characterized by performing various methods of measurements: current-voltage,
photoluminescence and photoresponse as a function of applied bias.
After developing the ability to grow multilayer
semiconductor quantum structures, GaAs/AlGaAs multiple
quantum wells (MQWs) have been intensively investigated
because of their potential applications in advanced optoelectronic
devices [1]. These studies resulted in a continuous
improvement of the performances and the appearance of novel
devices. In particular, infrared detectors based on intersubband
transitions in GaAs/AlGaAs MQW structures exhibit many
advantages over the conventional band-to-band HgCdTe
detectors, and represent an interesting alternative for the
detection of the mid- and far-infrared regions (i.e. wavelengths
longer than 3μm) [1,2].
The sample used in this study was grown by molecular beam
epitaxy (MBE) on (100) GaAs substrate. It consists of 10
periods of the following symmetric structure (from substrate
to top): 40 nm of AlGaAs (20% Al) barrier, 6 nm GaAs QW,
20 nm AlGaAs (20% Al), 10 nm graded AlGaAs (from 20%
to 25% Al), 10 nm AlGaAs (25% Al), 5 nm GaAs QW. This
10 repeat structure is sandwiched between a 6 nm GaAs QW
and thick doped contact layers. The central parts of the wells
are Si-doped to have the active carriers in the structures. The
top and bottom GaAs contact layers are 400 nm and 700 nm,
18 2
respectively and doped with 1×10P
P cmP P. Mesas were defined
by wet chemical etching and top and bottom contacts were
made by depositing Ge/Au/Ni/Au followed by annealing.
Different size square devices (400 m, 600 m, 800 m, 1000
m and 1500 m) having a ring top contact were fabricated to
test the uniformity of the wafer and the quality of the
fabrication. For the photoresponse (PR) measurements, sample
was mounted in a liquid nitrogen cooled dewar with ZnSe
window. A Bruker Equinox55 Fourier transform infrared
spectrometer with a globar source was used. A 7 mW HeNe
laser (632.8nm) was used as an excitation source in
photoluminescence experiments. For optical measurements,
devices were illuminated through the top opening. All
measurements were performed at a cold head temperature of
80 K.
I(A)
0.1
0.01
1E-3
1E-4
1E-5
80K
1500*1500m 2
1000*1000m 2
800*800m 2
600*600m 2
1E-6
-10 -8 -6 -4 -2 0 2 4 6 8 10
Voltage(V)
Figure 1. Current–voltage characteristics for the devices of different
sizes at 80K.
Current-voltage characteristics measured at 80K are shown
in figure 1. Figure 2 shows the PL signal coming from the
quantum well states under different bias values at 80 K. As
seen in figure 3, spectral photoresponse of the devices are in
7-12 m region as designed. And the response has voltage
dependence: the maximum signal was obtained when the
device is biased with 0.5 V.
PL Intensity(a.u.)
1000
900
800
700
600
500
400
300
200
100
0
0 volt
1 volt
2 volt
3 volt
730 740 750 760 770 780 790 800 810 820 830 840
Wavelength(nm)
Figure 2. Photoluminescence signal under different bias values at
80K.
Photoresponse (a.u.)
0.15 V
0.30 V
0.50 V
0.80 V
1.00 V
1.30 V
4 5 6 7 8 9 10 11
Wavelength (m)
Figure 3. Spectral photoresponse under different bias values at 80K.
In summary, we reported on the experimental
observations of a multilayer GaAs/AlGaAs QWIP.
Photoresponse measurements have shown that the devices are
working the intended spectral region: 8-12 m atmospheric
window. The voltage dependence of photoluminescence is
used to probe the energy levels involved in certain transitions.
This work was supported by TUBITAK under Grant No.
TBAG-107T012. We thank Prof. Dr. Atilla Aydnl and Prof.
Dr. Rait Turan for device fabrication and photoresponse
characterization steps.
*Corresponding author: hulya_kuru@hotmail.com
[1] Levine B.F.1993 J. Appl. Phys. 74 R1
[2]Liu H.C.2000 Intersubband Transitions in Quantum Wells:
Physics and Device Applications I, Semiconductors and Semimetals
vol 62 ed R. K. Willardson and E. R. Weber (San Diego: Academic)
pp129-96
80K
80K
6th Nanoscience and Nanotechnology Conference, zmir, 2010 627