WP2 Characterisation of Novel Materials for Avalanche Photodiodes

1. WP2 Characterisation of Novel Materials for Avalanche Photodiodes PROMIS Mid-term Review Meeting, London ESR : Shumithira Gandan Supervisors : Dr. Tomasz Ochalski & Dr. David Williams CIT @ Tyndall National Institute, Ireland 7th December 2016

2. Personal background • Beng (Hons) Electrical and Electronics Engineering, Malaysia • MSc Electrical and Electronics majoring in Photonics, Malaysia

3. Project title Optical characterization of novel Avalanche Photodiode (APD) samples. Aim To obtain information from APD samples with various spectroscopy techniques such as photoluminescence (PL), time resolved photoluminescence (TRPL), modulation spectroscopy and spectral elipsometry Deliverables • Carrier dynamics and bandgap structure of the quartenary alloy. • Identification of possible defects and their activation energy to define the non-radiative recombination channels.

4. Background of project Matter Photoluminescence Electrical energy (laser) Energy Spectroscopy – Experimental techniques to measure the interaction of light with matter Incident light ray Transmission Absorption Reflection Scattering -- Filter -- Passes part of the spectrum --Detector-- -- Sample -- Converts incident photons to different wavelength Photonics – Physics of interaction of light with matter Novel quartenary materials for Avalanche Photodiodes - AlGaAsSb Samples tested

5. Photoluminescence spectroscopy Involves photoexcitation of the sample using a laser source so that the emission from the sample can be read and interpreted. • Temperature dependent PL experiments for four samples of Al1-xGaxAsSb, x = 0, 5, 10, 15 • Samples are placed in a cryostat and cooled to very low temperatures (7-10K) and heated slowly with measurements taken at each interval • Information: wavelengths at which radiative recombination occurs Intensity (a.u) Wavelength (nm) Wavelength (nm) Temperature (K)

6. Power dependence of Ga 15% at 7K Intensity (a.u) Wavelength (nm) Power dependent PL measurements are done to determine the most suitable power for sample excitation. Setup for PL and TRPL

7. Laser repetition rate Time resolved photoluminescence spectroscopy Involves spectral and temporal evolution of the emission of a sample following its illumination by a short pulse of light. High Laser repetition rate Low

8. Intensity of emission proportional to the number of photo-generated carriers • Information: transition energies, carrier lifetimes • Decay times reflect recombination rates and reveals quality of crystalline structure • Presence of impurities and defects significantly reduce decay times Wavelength(nm) Time(ps) Streak image of measured AlGaAsSb at 830nm and 7K Decay times of temperature dependent TRPL

9. Photoreflectance & Electroreflectance spectroscopy • A spectroscopy technique that allows probing of the electric field of the sample through electromodulation • Information: bandgap structure and alloy composition particularly in quartenary compounds Setup for PR

10. Collaboration with other WPs 1. WP1 - GaAsN/GaAsN:H Quantum dots - Sapienza Universita’ di Roma 2. WP3 - GaSbN Quantum dots in intermediate band semiconductors for solar cells - Lancaster University 3. WP4 - InAsSb/GaSb and plasmonics for high sensitivity chemical and bio-sensing - Universitè Montpellier 2 GaAs GaAs: cap 100nm GaAs: spacing Layer “0,3,5,40nm” QD stack (x10) GaAsN:H GaAsN GaSb QDGaSb GaAs: buffer 100nm n doping GaAs (Si) substrate

11. Summary • Different optical characterization techniques have been used to investigate the physical parameters and quality of the grown APD samples. • Continued characterization will provide a complete understanding of the Al1- x GaxAsSb layers and allow feedback to University of Sheffield for optimizing growth of the sample layers for APD fabrication. • TRPL, PL and autocorrelation characterization of GaAsN/GaAsN:H quantum dot samples from SapienzaUniversita’ di Roma was also done to provide feedback on quality of samples.

12. Skills acquired • Advanced optical techniques in photoluminescence, time-resolved • photoluminescence, and modulation spectroscopy • Ridge waveguide laser fabrication process • Cryogenics and vacuum technology • 2 week secondment in University of Sheffield; • Basic electrical characterization of avalanche photodiode samples, • including IV, CV and X-ray absorption spectrum analysis. • Analysis of the rationale behind choosing specific parameters for the • APD materials • Courses : Key Enabling Technologies (KETs) workshop, Photonic Devices and • Materials, Advanced Characterization of Materials, Laser safety, Cryogenics • safety training

13. Outputs Poster presentation Effect of Gallium composition in AlGaAsSb alloys for APDs S. Gandan, J.S.D. Morales, X. Zhou, C.H. Tan, J.S. Ng and T.J. Ochalski, 19th International Conference on Molecular Beam Epitaxy, Montpellier (2016) Oral presentation Optical characterization of natural and CVD diamonds and diamond nano-particles; emission dynamics studies Tomasz J. Ochalski, H.Ye, D. Saladukha, J. Morales, S. Gandan 33rd International Conference on the Physics of Semiconductors, Beijing (2016) Optical spectroscopy of P-GaAs nanopillars on Si for monolithically- integrated light sources J.S.D Morales, S. Gandan, D. Ren, D. L. Huffaker, T. J. Ochalski, SPIE, Photonics West Conference & Exhibition, San Francisco, California (Jan 2017)

14. Future work • N umerical analysis of PR/ER spectra with Third Derivate Lineshape (TDLS) and Airy function line shape fitting to derive accurate bandgap information and broadening parameters of APD samples. • Spectroscopy and analysis of samples from collaborations. • Hosting of planned secondments • 28th November – 3rd December 2016 • ESR 14 from Universitè Montpellier 2 (Mario Bomers) • Within the next month • ESR 9 from Lancaster University (Denise Montesdeoca Cardenes) • Planned secondments • Universitè Montpellier 2 (May 2017) • University of Sheffield (2017)

15. Aspirations • Industry position in photonics sector related to optical characterization techniques. • Academic position in a topic to further investigate physics related to spectroscopy.