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!