Self-Organization of InAs/InP Quantum Dot Multilayers

1
Self-Organization of InAs/InP Quantum Dot
Multilayers

• Navdeep Singh Dhillon

2
Overview

• Regimes of 3-D self-organization in quantum dot
  layers described using
• Experimental observations for InAs/InP(001)
  system
• Atomistic Strain calculations
• Pseudophase diagram developed to explain
  transition from vertically aligned to
  anti-aligned layers

3
Motivation

• Periodicity and size uniformity of quantum dots
  grown in Stranski-Krastanov mode important for
  device applications
• Detailed understanding of physical origin of
  phenomena prerequisite for obtaining the required
  3-D arrangement for particular application

4
Stranski-Krastanov growth

• Low-Pressure Metal-Organic Vapor Phase Epitaxy in
  a cold-wall reactor

InP(001) substrate
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Stranski-Krastanov growth
3-7 ML of InAs is deposited
InAs
InP substrate
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Stranski-Krastanov growth
60 s treatment in TBAs/H2 ambient
InAs Islands
InP substrate
The InAs monolayers form islands due to
Interlayer Strain
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Stranski-Krastanov growth
Deposit Spacer layer and repeat
InAs Islands
InP substrate
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2 Regimes of Self-organization
Vertically Aligned (VA)
Anti-Aligned (AA)
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Quantum Dot Array Modeling
H Spacer Thickness h QD heigth b QD
base D Lateral Spacing
C Vertically aligned point A1, A2,
A3 Anti-aligned points
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Experimental Results

• Alignment depends mainly on H/D
• Slight dependence on b/D
• No direct dependence on h

11
Atomistic Strain Calculations

• Keatings valence force field method
• Atomic coordinates relaxed using a
  conjugate-gradient algorithm until a minimum of
  elastic energy is found
• 16.6 lt D lt 29 nm
• 3.3 lt b lt 15.8 nm
• 1.2 lt h lt 3.6 nm

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Conclusions

• Self-organization of quantum dot multilayers
• Spacer layer thickness (H)
• Areal density of islands (D)
• Lateral dimension (b) (to a lesser extent)

H
b
D