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FABRICATION AND CHARACTERIZATION OF

Au/n-Si/Au METAL SEMICONDUCTOR METAL

STRUCTURE

By

SOUMO GHOSALSHRABANI SAMADDAR

204/11/23

Detector Technologies

MSM( Metal Semiconductor Metal)

PIN

APD

Waveguide

Contact InP p 1x1018

Multiplication InP n 5x1016

Transition InGaAsP n 1x1016

Absorption InGaAs n 5x1014

Contact InP n 1x1018

Substrate InP Semi insulating

Semiinsulating GaAs

Contact InGaAsP p 5x1018

Absorption InGaAs n- 5x1014

Contact InP n 1x1019

Absorption Layer

Guide Layers

Simple, Planar, Low CapacitanceLow Quantum Efficiency

Trade-off Between Quantum efficiency and Speed

High efficiencyHigh speedDifficult to couple into

Gain-Bandwidth: 120GHzLow NoiseDifficult to makeComplex

Key: Contact layers

Layer Structure Features

Absorption Layer

3

MSM Detectors

Semi insulating GaAs

Simple to fabricate

Quantum efficiency: MediumProblem: Shadowing of absorption region by contacts

Capacitance: Low

Bandwidth: HighCan be increased by thinning absorption layer and backing with a non absorbing material. Electrodes must be moved closer to reduce transit time.

Compatible with standard electronic processes

GaAs FETS and HEMTs InGaAs/InAlAs/InP HEMTs

To increase speeddecrease electrode spacingand absorption depth

Absorptionlayer

Non absorbing substrate

E Fieldpenetrates for ~ electrode spacinginto material

Simplest Version

Schottky barriergate metal

Light

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4

Schottky Contacts and Ohmic Contacts Compared

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Schottky contact is to GaAs doped at 1015 cm-3

Ohmic contact resistance is 104 Ωcm2.

Contacts satisfy Ohm's law. Semiconductor is very highly doped. Schottky barrier depletion region very thin depletion layer becomes quite transparent for electron tunneling.Better to use a metal with a work function m, which is equal to or smaller than the work function of a semiconductor, s.

504/11/23

A Comparative Study of Si and GaAsMetal-Semiconductor-Metal Photodetectors

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BEAKER CLEANING

WAFER CLEANING DI water and ultrasonically agitation. Boiled with hot (TCE) at 80 to 850C for 10-15min. TCE is removed by acetone. Acetone is removed by rinsing with DI water. Soln of NH4OH , H2O2 and H2O at the ratio of 1:1:8 , and kept it for 10-15 minutes at 80 to 850C & then rinsed with DI water A solution (8 : 2 : 1 parts by volume of H2O : H2O2 : HCl ) at 60-70oC for about 10 minutes to remove heavy metals. Dipped for few seconds in 10% solution of HF to remove the SiO2 layer. Cleaned with DI water to make it hydrophobic.

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WAFER SPECIFICATIONS :

Crystal Orientation: <111>[n-type]Substrate resistivity: 1.5 ohm cmWafer thickness: 300 25 μm

The Ultrasonic Vibrator

+-

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METALLIZATION

HIGH VACUUM CREATIONDEPOSITION OF METAL ON ONE SIDE RETURNING TO NORMAL CONDITIONS DEPOSITION OF METAL ON OTHER SIDE

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Electron Beam Generator Penning Gauge Metallization Unit

Vacuum ChamberVacuum Measuring Gauges

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PHOTOLITHOGRAPHY & ETCHINGWafer is subjected to photoresist(-ve) and then it was rotated at 2500rpm in a photoresist spinner .

Wafer heated at a temperature of 100 ºC for 15 min in a hot air oven to increases the resist adhesion to wafer. Exposed to U-V light through a photomask for 5 mins. Under exposition of light, the wafer became hard.

Dissolved in developer solution

Removal of the developer by rinsing .

Post-baked in order to dry-out for at least 20 min at 125ºC. Post- baking makes the image permanent.

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The Circuit set up for I-V Measurement

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IV Characteristics of MSM structure with and without Illumination

-80

-60

-40

-20

0

20

40

60

80

-0.5 -0.4 -0.3 -0.2 -0.1 0 0.1 0.2 0.3 0.4 0.5 0.6

Voltage (V)

Cu

rren

t (m

A)

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CV Characteristics

0

200

400

600

800

1000

1200

0 2 4 6 8 10 12 14 16 18 20

Bias Voltage (volts)

Cap

acit

ance

(p

F)

Characterization

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The FESEM Instrument used at IACS, Jadavpur for study of surface morphology

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Surface Characterisation

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Cross Sectional SEM

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Cross Sectional View of the lower junction

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EDAX analysis of Pos1 showing presence of Au,Cr and Si

20

Qualitative and Quantitative Analysis of Pos1 of the

Sample

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21

Bibliography

1. Chou, S. Y., Liu, Y. and Fischer, P. B., Appl. Phys. Lett. 61,477 (1992).

2. Physics of Semiconductor Devices, Second edition, S. M. Sze, Wiley & Sons, 1981, Chapter 5.

3. Device Electronics for Integrated Circuits, Second edition, R.S. Muller and T. I. Kamins, Wiley & Sons, 1986, Chapter 3. 4. Physica Scripta. Vol. T69, 163-166, 1997 A Comparative Study of Si and GaAs Metal-Semiconductor-Metal Photodetectors K. Honkanen,' T. Siirtola,' T. Majamaa,' A. Hovinen' and P. Kuivalainen','

5. “Fabrication and modelling of SOI and GaAs MSM Photodetectors and GaAs based photreceivers.” - Dissertation for the degree of Doctorate in Technology by Katri. Honkanen, Helsinki University of of Technology.

6. “Current transport in Metal – semiconductor Barriers”-C. R. Crowell & S. M. Sze solid state electronics , 9, 1035 . ( 1966 )

7.Solid State Electronic Devices. B .G .Streetman

8. Semiconductor Opto-Electronic Devices .Pallab Bhattacharya 04/11/23

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