fabrication and characterization of n-zno/p-si heterostructure
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FABRICATION AND CHARACTERIZATION OF n-ZnO
/ p-Si HETEROSTRUCTURE
BY
NUR ATIQAH BINTI MASRI
109261Applied Science (Engineering Physics)
Supervisor : DR. Ng Sha ShiongExaminer : DR. Mutharasu Devarajan
School of Physics, Universiti Sains Malaysia (USM), 11800 Minden, Penang, Malaysia.
Presentation’s Agenda
1. Introduction2. Objectives3. Definitions4. Literature Review5. Methodology6. Observations and Results7. Conclusion
Introduction
Background of Heterostructure A structure that has junctions between
different bandgap materials or a structure that made from a
heterojunction Advantages of n-ZnO
Wide direct optical bandgap Large exciton binding energy Large melting point Strong anti-radiation damaging ability
Advantages of p-Si Cheap Easier to cleave than that sapphire
Advantages of n-ZnO/p-Si Used for fabrication of solar cells and
optoelectronic devices
Objectives
To fabricate n-ZnO thin film on p-Si substrate by radio frequency (RF) sputtering.
To investigate the structural and electrical properties of the n-ZnO/p-Si heterojunction.
Definition
Depletion region, W - the regions of accumulation of net positively charge and negatively charged.
Literature Review
1. The properties of ZnO is depent on film thickness as well as properties of heterojunction.
Mridha, S., M. Dutta, and D. Basak
2. ZnO/Si heterojunction exhibit a good rectifying behaviour. Ocak, Y.S., and Chen, T., et al., and Xiao-Yun, T., et al., and Song, D., et al.,
and Zebbar, N., et al.
3. The small deviation from the ohmic behaviour indicates that the transport mechanism depends on the nature of contacts.
Zebbar, N., et al.
4. The smaller the FWHM, the higher the film’s crystallinity Qi, H., et al.
Methodology
Sample Preparation
ZnO thin film is deposited on p-type Si by RF
Sputtering
Characterizations
Structural Properties
XRD
To measured
the crystalline
structure of the ZnO film
FESEM
To view the surface
morphology of sample
To determine the thickness of the
sample
AFMTo scan the specimen surface
To determine the topography and
other properties of sample surfaces
Electrical Properties
Contact Characteristics
Al Contact
Annealing Process
To get ohmic (annealing
process at 550°C for 20 mins using
grey furnace)Hall Effect measurements
I-V and C-V Characteristics of
PN Junction
Observations and Results
STRUCTURAL CHARACTERIZATIONS
XRD
To identify crystalline phases and orientation.
Showed three peaks :-(a) Si (111) at 28.75(b) ZnO (002) at 34.15 - highest peak(c) ZnO (004) at 71.94
The smaller the FWHM, the higher the crytallinity and the better the quality of the sample.
FESEM
To analyse the film thickness and surface morphology of the sample.
The image of surface is analysed by two different magnification (30 kx and 100 kx) to obtain the clearer image of sample’s surface.
Results Granular shape of particles Thickness of wafer = 505.8 nm
AFM
To determine the roughness, height steep measurement and image surface of sample.
Results RMS = 0.00513 m highness of peak = 20.9 nm
ELECTRICAL CHARACTERIZATIONS
I-V and C-V Characteristics
To obtain ohmic for contacts from I-V curve
To obtain the rectifying behaviour for the heterojunction.
To determine the ideality factor, barrier height and width of depletion region.
Ohmic contact
Not symmetry because of the differences in surface’s condition
p-n junctions
I-V curve
Io = 2 x 10-6 A, 𝜱b = 0.86 eV , n = 3.26, W = 386.9 nm
C-V curve
Vbi = 0.65 eV , 𝜱b = 0.81 eV , W = 402.7 nm
Hall effect measurements
To obtain the carrier and holes concentration of the samples.
Electrons concentration, Nd : 1.83 1016
cm3 ; Hall mobility : 1.28 cm2/Vs Holes concentration, Na : 4.81015 cm3 ;
Hall mobility : 270 cm2/Vs.
CONCLUSIONS
Not an ideal diode.
Barrier height of this heterojuction that is obtained from C-V curve, 0.05 eV lower than that obtained from I-V curve.
Width of depletion region obtained from C-V curve 15.8 nm higher than that I-V curve.
The differences of barrier height and width of depletion region obtained from I-V and C-V measurements are results of the different technique used.
THANK YOU!
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