Mater. Res. Soc. Symp. Proc. Vol. 1805 © 2015 Materials Research Society
DOI: 10.1557/opl.2015.
Effect of Nitrogen implantation on the optical characteristics of Zn
0.85
Mg
0.15
O thin film at
low temperature
S. Saha, S. Nagar and S. Chakrabarti
1
1
Department of Electrical Engineering
Indian Institute of Technology Bombay
Powai, Mumbai 400076, India
ABSTRACT
The importance of Zn
x
Mg
1-x
O is increasing day by day because of its wider bandgap than
ZnO. This ternary semiconductor finds its application in the fields of optoelectronics,
spintronics, superlattices due to its unique blueshifted UV-luminescent property. n- to p-type
conduction which is the motive of the project can be achieved with increasing Mg content in
ZnMgO. The optical characteristics of the nitrogen doped Zn
x
Mg
1-x
O (x=0.85) grown on 2 inch
Si <100>wafer by RF sputtering are studied and analyzed thoroughly using low temperature
(15K) photoluminescence measurements. Nitrogen implantation was carried out by Plasma
immersion Ion Implantation technique on the sample. Rapid Thermal Process was employed to
remove defects resulting from implantation. The samples were annealed at 700°C, 800°C,
900°C, and 1000
o
C for 10 seconds in an oxygen ambient. Photoluminescence (PL)
measurements were performed at low temperature (15K) which exhibited acceptor-bound-
exciton peak (A˚X) and donor-bound-acceptor pair (DAP) at 3.336 eV and 3.236 eV
respectively. At 3.364 eV, S peak was found for the sample annealed at 800
˚
C after implantation.
This peak was attributed to the existence of ZnO-like composition. Localized and de-localized
exciton peaks were found around 3.42 and 3.45 eV respectively. This result is very important
because though dominant acceptor peak was not found but proper optimization of the parameters
can lead to p-type ZnMgO which is the main motive of this project.
INTRODUCTION
ZnO, with a wide band-gap of 3.37 eV and large exciton binding energy of 60 meV at
room temperature, has been one of the most important semiconductors in recent years in the area
of optoelectronic devices, [1]. Due to its high exciton binding energy it has excellent excitonic
effects from room temperatures to 550K as reported by Ohtomo et al.[2]. So, ZnO is regarded as
the most promising choice for the next generation ultraviolet light emitting devices. Several
growth methods like MBE [3], MOCVD [4], PLD [5], sputtering [6] processes are employed for
the growth of ZnO. It can be used in solar cells [7, 8], light-emitting devices [9], gas sensors
[10], thin film transistors [11]. However, bandgap engineering is necessary to increase the
bandgap of ZnO in order to achieve material like ZnMgO which can be used as barrier material
for quantum well, HEMT devices. It has already been proved by several researchers that
incorporation of MgO in ZnO can increase the band gap by shifting the conduction band edge
upward, thus increasing the distance from the intrinsic shallow donor states, which essentially
increases the activation energy of the defect donors of ZnO. The ionic radius of Mg
2+
(0.57 Å)
and Zn
2+
(0.60 Å) also are very close to each other. However, during growth , keeping the lattice
682