Appl. Phys. A (2014) 116:193–197
DOI 10.1007/s00339-013-8082-8
Structural, surface, and electrical properties of nitrogen
ion implanted ZnTe epilayers
Qiumin Yang · Chao Liu · Lijie Cui ·
Linen Zhang · Yiping Zeng
Received: 2 September 2013 / Accepted: 14 October 2013 / Published online: 19 November 2013
© Springer-Verlag Berlin Heidelberg 2013
Abstract P-type ZnTe epilayers grown on GaAs (001)
by molecular beam epitaxy have been achieved by N ions
implantation, and reached a doping level of more than
1 × 10
18
cm
−3
. X-ray diffraction spectra suggest that increas-
ing the post-implantation annealing temperature can pro-
mote the N ions occupying substitutional sites and help to
remove the radiation damage.The hole concentration rises
with annealing temperature, while the lowest resistivity and
the highest mobility can be obtained by annealing at 450
◦
C
for 5 min. Annealing for 1 min cannot obtain low resistiv-
ity. Fabricating ZnTe films with a lower VI/II beam equiva-
lent pressure ratio results in an enhancement in hole concen-
tration and a drop of mobility.In addition, p-ZnTe/n-GaAs
and p-ZnTe/n-ZnSe/n-GaAs junctions show better rectifying
behaviour after ion implantation.
1 Introduction
ZnTe is a zinc-blende structure II-VI compound semicon-
ductor with a direct band-gap of 2.26 eV at room tem-
perature, which makes it suitable to fabricate green light
emitting diodes (LED) [1–3]. Recently, Zhang et al. pro-
posed the utilization of ZnTe as top cell in a monolithic
integrated multijunction solar cell [4], and other researchers
explored the intermediate-band photovoltaic solar cell based
on ZnTe:O [5]. In addition, ZnTe has potential applications
in wave-guides and terahertz (THz) devices [6,7]. As ZnTe
Q. Yang (
B
) · C. Liu · L. Cui · L. Zhang · Y. Z en g
Key Laboratory of Semiconductor Materials Science,
Institute of Semiconductors, Chinese Academy of Sciences,
100083 Beijing , China
e-mail: qiuminyang@semi.ac.cn
Y. Z e ng
e-mail: ypzeng@red.semi.ac.cn
is unipolar compound semiconductor, p-type ZnTe layer is
relatively easy to achieve. Several works have obtained p-
type ZnTe thin films successfully by different techniques
including molecular beam epitaxy (MBE) with nitrogen
plasma source [8], metalorganic chemical vapor deposition
(MOCVD) using trimethylarsine [9], and pulsed laser abla-
tion in molecular nitrogen [10]. Besides those techniques
above, diffusion and ion implantation are widely used for
preparing doped semiconductor thin films. The ion implan-
tation technique is better control and more accurate than the
diffusion technique [11]. Moreover, ion implantation is a suit-
able technology for selective area doping in planar devices
[12]. Although the defects created by ion implantation need
to be removed using rapid thermal annealing, ion implanta-
tion can maintain a relatively sharp interface due to the short
annealing duration compared with diffusion process. How-
ever, very few of studies focus on preparing p-type ZnTe by
ion implantation.
In this paper, ZnTe thin films were grown by MBE
and doped by nitrogen ion implantation. The influences of
implantation and annealing on the crystalline quality, sur-
face morphology, and electrical properties of ZnTe epilayers
are investigated. In addition, the effects of ion implantation
on ZnTe/GaAs and ZnTe/ZnSe junctions are presented.
2 Experiments
The unintentionally doped ZnTe epilayers were grown on
semi-insulation GaAs (001) substrates by MBE using ele-
mental Zn (6 N) and Te (6 N) as source materials. The sub-
strate temperature has been optimized and fixed at 360
◦
C
for single-polished substrates [13] or adjusted to 390
◦
Cfor
double-polished substrates. The VI/II beam equivalent pres-
sure (BEP) ratio (R
VI/II
) was varied in the range of 3.0–8.0.
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