Modelling Dilute Nitride Semiconductors (PROMIS Mid-term Review Meeting) Reza Arkani Supervisor: Eoin O’Reilly

My specific background BSc in Electrical Engineering (Magneto-therapy) Karaj University Laser & Plasma Research Institute MSc in Photonics (Performance Enhancement of Thin-film Silicon Solar Cells Using Photonic Crystals)

My specific background I joined Tyndall National Institute on November 2015 to start my research in Photonics Theory Group. Demonstrating undergraduate module courses in Department of Physics, University College Cork

My role in PROMIS project Modelling of dilute nitride quantum wells and quantum dots

Dilute nitride semiconductors In dilute nitride materials, localised Nitrogen resonant states reduce the band gap energy, and effectively cause the conduction band to split into two non-parabolic sub-bands leading to flexible wavelength tailoring. Band Anti-Crossing (BAC) model provides a good basis to understand the electronic properties of nitride alloys. Dispersion relation for GaN0.005As0.995 calculated by BAC model Tomić, S., et al. , Physical Review B 69.24 (2004): 245305. Shan, w., et. al. , Physical Review Letters 82 (1999): 1221.

Introduction to S/PHI/nX is a software package which uses continuum elasticity theory and multiband k.p model for opto-electronic properties of quantum nano-structures. 2-band BAC: for conduction band (CB) 10-band BAC: for valence band (VB) O. Marquardt, “Tutorial based on S/PHI/nX 2. 0. 2”, 2012 Gladysiewicz, M., et. al., Journal of Applied Physics 113.6 (2013): 063514.

Quantum well calculation by 2-band & 10-band BAC model Bold lines: 2-band BAC Dashed lines: 10-band BAC Well width dependence of the transition energies of GaN0.02As0.98

Simulation of strained QW structures GaAs InGaAsN Hydrostatic component Biaxial strain CB = 1.42 GaAs In0.35Ga0.65As0.98N0.02 GaAs CB = 1.14 CB = 1.04 δECBhy ΔEC = 0.29 e1 = 0.063 Energy (eV) Energy (eV) e1–hh1= 1.103 (1.13 μm) Eg = 1.42 VB = 0.11 δEVBhy ηaxhh HH = 0.10 VB = 0 ηaxlh LH = 0.08 SO = -0.25 ΔEV = 0.10 hh1 = 0.006 δEVBhy SO = -0.34 ηaxso SO = -0.27 Sketch of strain-related shifts in CB and VB of In0.35Ga0.65As0.98N0.02/GaAs. Confinement potential for 8 nm wide In0.35Ga0.65As0.98N0.02/GaAs QW.

Simulation of Quantum Dots 6 nm 6 nm 6 nm Sketch of a GaN0.02As0.98/GaAs QD E = 1.24 eV E = 1.33 eV

Summary Studies on BAC model Learning how to use S/PHI/nX as a powerful tool for quantum nano-structures calculations QW band structure calculations using both 2-band & 10-band BAC model QD band structure calculations using 2-band BAC model

Skills acquired Coding in Matlab and C Application and use of freeware S/PHI/nX, including testing and learning how to deal with the bugs Attended three courses in UCC: Advanced Computational Physics Advanced Condensed Matter Physics Post-graduate Teaching & Demonstrating Module

Poster presentation in Tyndall Poster Competition, July 2016 Outputs Poster presentation in Tyndall Poster Competition, July 2016 Poster presentation in the MBE Conference 2016 (as a part of PROMIS), September 2016

Outlook Future works: Aspirations: Optimising the electronic and optical properties of GaSbN QD’s for CPV solar cells grown by Lancaster University (WP3) Designing and optimising the emission characteristics of Type-II InAsSbN/InAs/AlAsSb structures grown by Lancaster University for mid-IR LED applications (WP4) Modelling hydrogenated dilute nitride semiconductors (WP1) Aspirations: Industry/academic position in which I can use my knowledge, specifically optimisation studies in Photonics

Thank you for your attention