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SEMINAR PRESENTATION ONSEMINAR PRESENTATION ON

MOVCD TECHNOLOGYMOVCD TECHNOLOGY

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MOCVD technology and material growth

1.Introduction

2.The MOVD technique and growthsystem

3.Metalorganic compound

4.Gas phase and surface reaction

5.Materials Characterization

6.MOCVD growth of GaN

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Most of the advances in semiconductor processing havecentered on the ability to decrease the physical dimensionsof the electronic device structure.

Lateral dimension

Photolithographic,Deposition

Etching techniques Vertical dimension:

Epitaxial deposition

1.Introduction

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. The MOVD growth system

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MOCVD Growth System

Vacuum and

Exhaust system

Gas handlesystem

ComputerControl

Reactor

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MOVCD REACTORS

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Discretionary Access Control (DAC)

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Aixtron Model-2400 reactor

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3. Metalorganic compound

The vapor pressure of the MO source is an importantconsideration in MOCVD, since it determines the concentration ofsource material in the reactor and the deposition rate. Too low avapor pressure makes it difficult to transport the source into thedeposition zone and to achieve reasonable growth rates. Too high

a vapor pressure may raise safety concerns if the compound istoxic. Further more, it is easier to control the delivery from aliquid than from a solid.

Vapor pressures of Metalorganic compounds are calculated interms of the expression

Log[p(torr)]=B-A/T

separately

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4. Gas phase and surface reaction The basic reaction describe GaN growth can simply write as

Ga(CH3)3+NH3 GaN+3CH4

The growth procedure as follows:

MO sources and hydrides inject to the reactor.

The sources are mixed inside the reactor and transfer to thedeposition area

At the deposition area, high temperature result in thedecomposition of sources and other gas-phase reaction, formingthe film precursors which are useful for film growth and by-products.

The film precursors transport to the growth surface The film precursors absorb on the growth surface The film precursors diffuse to the growth site At the surface, film atoms incorporate into the growing film

through surface reaction The by-products of the surface reactions absorb from surface The by-products transport to the main gas flow region away from

the de osition area towards the reactor exit

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reaction

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5. Materials Characterization

Physical characterization X-ray diffraction (XDS)

Transmission electron microscopy (TEM)

Optical microscopy

Scanning electron microscopy (SEM)

Atom force microscopy (AFM)

Secondary ion mass spectroscopy (SIMS)

Electrical Measurements

Van der Pauw Hall

Capacitance-voltage (C-V)

Optical measurements

Photoluminescence (PL)

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6. MOCVD grow GaN and related

materials

High temperaturetreatment

Bufferlayer

EpilayerGrowth

TMGa

NH3

Temperature

1150oC

550oC

1050oC

Two Step MOCVD Growth procedure

Ga(CH3)3+NH3 GaN+CH4

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Some basic problem related to GaN

growthMOCVD and other epitaxialtechniques have developed morethan 30 years, but high quality GaNand related compound only availablein recent years. There are some

special problems for GaN and relatedmaterials.

No suitable substrate

Difficult to obtain p-type epilayer

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THANK YOU