Metal Contacts for the Hybrid Silicon Laser Morgan Swaidan, Ventura - - PowerPoint PPT Presentation

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Metal Contacts for the Hybrid Silicon Laser Morgan Swaidan, Ventura - - PowerPoint PPT Presentation

Feb 13, 2023 48 likes •258 views

Metal Contacts for the Hybrid Silicon Laser Morgan Swaidan, Ventura College Major: Physics Mentor: Siddharth Jain Faculty Advisor: Dr. John Bowers Funding Agency : Intel Corp Department of Electrical and Computer

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SLIDE 1

Metal Contacts for the Hybrid Silicon Laser

Morgan Swaidan, Ventura College

Major: Physics Mentor: Siddharth Jain Faculty Advisor:

  • Dr. John Bowers

Funding Agency : Intel Corp Department of Electrical and Computer Engineering

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SLIDE 2

Outline

  • Optical communication
  • Hybrid Silicon Laser

– Need for metal-semiconductor contacts

  • Measurement technique

– Two and four point probe method

  • Anatomy of a metal contact
  • Measurement results

2

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SLIDE 3

3

Optical Communication

Fiber optic cables

  • For long distance communication
  • Niche technology
  • Expensive components

What we want

  • Adapt technology to everyday use
  • Eg. Faster internet

Why is it important

  • Replace existing copper cable
  • Fast & efficient data communication

Make cheaper/better light sources

Fiber optic cable array

UK USA

Trans-Atlantic cable

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SLIDE 4

4

Outline

  • Optical communication
  • Hybrid Silicon Laser

– Need for metal-semiconductor contacts

  • Measurement technique

– Two and four point probe method

  • Anatomy of a metal contact
  • Measurement results

4

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SLIDE 5

Hybrid Silicon Laser

5

Indium Phosphide (light-producing) Silicon

Aim: Convert electrical energy  light energy

Metal Current Light

Metal Semiconductor Problem: “Usual” gold contacts incompatible with Si What we’ll do: Study metal/semiconductor interface

  • Try other metals
  • Which has lowest resistance?
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SLIDE 6

Outline

  • Optical communication
  • Hybrid Silicon Laser

– Need for metal-semiconductor contacts

  • Measurement technique

– Two and four point probe method

  • Anatomy of a metal contact
  • Measurement results

6

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SLIDE 7

What Do We Want to Measure?

We want Rc: Contact Resistance

– Rs: Inherent resistance of semiconductor

What we actually record: Specific contact resistance (ρ) – takes into account area through which current flows.

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Metal Semiconductor

Rc

Rs

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SLIDE 8

Measuring Resistance

  • We want to measure Rc
  • Measured Resistance = 2Rc + Rs

8

Rc Rc Rs x Ω i

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SLIDE 9

Finding Contact Resistance (Rc)

  • Rs depends on spacing (x)
  • Vary spacing to construct graph

9

x

x x R total y-int = 2Rc Spacing Rt = Rs(x) +2Rc

semiconductor metal

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SLIDE 10

Two Point Probe Method

i Ω

Ω

Rn Rn Rc Rc Rs

Rn=needle resistance Rc=contact resistance Rs=semiconductor resistance

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SLIDE 11

11

Four Point Probe Method

i A

A

Rn Rn Rc Rc Rs V V i Rn Rn i = 0

Rn=needle resistance Rc=contact resistance Rs=semiconductor resistance

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SLIDE 12

Outline

  • Optical communication
  • Hybrid Silicon Laser

– Need for metal-semiconductor contacts

  • Measurement technique

– Two and four point probe method

  • Anatomy of a metal contact
  • Measurement results

12

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SLIDE 13

Anatomy of a metal contact

13

Semiconductor Adhesion layer Dopant layer Barrier layer Thick metal layer

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SLIDE 14

14

Anatomy of a metal contact

14

InP Palladium (Pd) Germanium (Ge) Tungsten (W) Aluminum (Al)

On Indium Phosphide (InP):

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SLIDE 15

15 15

Anatomy of a metal contact

15

InGaAs Titanium (Ti) X Tungsten (W) Aluminum (Al)

On Indium Gallium Arsenide (InGaAs):

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SLIDE 16

16

Outline

  • Optical communication
  • Hybrid Silicon Laser

– Need for metal-semiconductor contacts

  • Measurement technique

– Two and four point probe method

  • Anatomy of a metal contact
  • Measurement results

16

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SLIDE 17

Non-annealed samples

17 10 20 30 10 20 30 14 16 18 20 5 10 15 20 25

Ti/W/Al on InP Pd/Ge/Pd/W/Al on InP

Resistance (Ω) Resistance (Ω) Spacing (μm) Spacing (μm)

Some samples not even linear  non-linear = not Ohmic [Ohmic: V = iR]

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SLIDE 18

Non-annealed samples

18

  • 0.8
  • 0.4

0.4 0.8

  • 5

5

Pd/Ge/Pd/W/Al

Current (Amp) Voltage (V)

  • 0.2
  • 0.1

0.1 0.2

  • 4
  • 2

2 4

Current (Amp) Voltage (V)

Ti/W/Al

Ohmic: Linear relationship between voltage and current (Contacts must be Ohmic)

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SLIDE 19

19

  • 0.4
  • 0.2

0.2 0.4

  • 4
  • 2

2 4

Ti/W/Al

Current (Amp) Voltage (V)

  • 1.2
  • 0.8
  • 0.4

0.4 0.8 1.2

  • 3
  • 2
  • 1

1 2 3

Pd/Ge/Pd/W/Al

Current (Amp) Voltage (V)

Annealed at 350°C, 30 sec

After annealing, both samples are Ohmic

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SLIDE 20

Which contact has lowest resistance?

20

  • 2

2 4 6 8 10 12 14

  • 5

5 10 15 20 25

Spacing (μm) Resistance (Ω) Ti/W/Al Pd/Ge/Pd/W/Al ρ = 6.62 x 10-6 Ω-cm2 ρ= 9.50 x 10-7 Ω-cm2

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SLIDE 21

Looking ahead…

  • Two possible semiconductors: InP and InGaAs
  • Find contact that will work equally well on both

– Simplifies manufacturing

InP  lots of Germanium InGaAs less Germanium

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Resistance Amount of Germanium “Happy medium” InGaAs InP