Origin of two-step photon absorption in GaAs thin film by first-principles spin-orbit calculations and STM/STS measurements

Authors

Mary Clare Escaño Research Center for Development of Far-Infrared Region, University of Fukui, Japan

Abstract

Terahertz radiation, which lies between the microwave and infrared region of electromagnetic spectrum, coincides with excitation of many systems including biological systems, making it very attractive to biomedical imaging, security and low-energy spectroscopy, among others. However, the prevalent THz gap {roughly 100 GHz (0.1 THz) and 10 THz} exists for the lack of efficient THz radiation generators. Low-temperature GaAs (LT-GaAs) thin film is found to emit THz radiation when placed in a photoconductive antenna and hit by femtosecond laser pulse at 1560 nm pump pulse. This indicates a sub-band gap excitation and the emission is attributed two-step photon absorption (TSPA). Using first-principles method with spin-orbit interaction (DFT-SO) to account for the broken inversion symmetry of GaAs, we found that the TSPA is due to 1% As-antisite defect within the bulk of GaAs. To understand the atomic/electronic structure of this bulk defect, we employed theoretical and experimental STM/STS and found that the defect exhibits characteristic three level peaks in STS and an "asymmetric two-lobe" STM image on GaAs(110). These results pose new contributions not only to the development of terahertz emitter devices based on GaAs but also to the "atomic scale" imaging and characterization of a bulk defect in an otherwise high-resistance semiconductor surface.

About the Speaker

Mary Clare Escaño, Research Center for Development of Far-Infrared Region, University of Fukui, Japan

Mary Clare Escaño is an Associate Professor at the Research Center for Development of Far-Infrared Region, University of Fukui, Japan. She earned her Ph.D. in Engineering from Osaka University (OU) in 2012. Prior to her doctoral course, she obtained her Masters degree in Engineering from OU and Masters degree in Physics from De La Salle University, Manila. She explores and develops first-principles techniques to theoretically study materials for terahertz generation. She is interested in understanding the mechanisms and in revealing the new physics at surface/interfaces of these materials.

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Issue

2021: Proceedings of the 39th Samahang Pisika ng Pilipinas Physics Conference

Article ID

SPP-2021-INV-1B-01

Section

Invited Presentations

Published

2021-09-10

How to Cite

[1]

MC Escaño, Origin of two-step photon absorption in GaAs thin film by first-principles spin-orbit calculations and STM/STS measurements, Proceedings of the Samahang Pisika ng Pilipinas 39, SPP-2021-INV-1B-01 (2021). URL: https://proceedings.spp-online.org/article/view/SPP-2021-INV-1B-01.