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

5. Stranski-Krastanov growth 3-7 ML of InAs is deposited InAs InP substrate

6. Stranski-Krastanov growth 60 s treatment in TBAs/H2 ambient InAs Islands InP substrate The InAs monolayers form islands due to Interlayer Strain

7. Stranski-Krastanov growth Deposit Spacer layer and repeat InAs Islands InP substrate

8. 2 Regimes of Self-organization Vertically Aligned (VA) Anti-Aligned (AA)

9. 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

10. Experimental Results • Alignment depends mainly on H/D • Slight dependence on b/D • No direct dependence on h

11. Atomistic Strain Calculations • Keating’s valence force field method • Atomic coordinates relaxed using a conjugate-gradient algorithm until a minimum of elastic energy is found • 16.6 < D < 29 nm • 3.3 < b < 15.8 nm • 1.2 < h < 3.6 nm

12. 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