C. P. Sadia, L. P. Lopez, Jr., R. M. delos Santos, J. E. Muldera, A. E. De Los Reyes, M. A. C. Tumanguil, C. T. Que, V. K. Mag-usara, M. Tani, A. S. Somintac, E. S. Estacio, and A. A. Salvador

Thin Solid Films 648, pp. 46 - 49 (2018) [Ref]

We report the molecular beam epitaxy growth of high-quality p-InAs thin films evaluated in the context of 1.55 µm femtosecond laser-excited THz emission efficiency. The presence of p-InAs is confirmed via scanning electron microscopy and x-ray diffraction. Using a GaAs buffer layer, the epitaxial growth of p-InAs layers was successfully achieved. Initiating GaAs deposition by growth interruption, we find that GaAs adheres to the GaSb substrate and provides a quasi-planar surface for the subsequent layers. We also find a significant enhancement in the THz radiation intensity of p-InAs films that is approximately twice compared to that of bulk p-InAs for 1.55 µm wavelength.

Copyright 2018 Elsevier


C. P. Sadia, J. Muldera, E. S. Estacio, A. S. Somintac, A. A. Salvador, C. T. Que, K. Yamamoto, and M. Tani

Applied Physics Express 8, 035501 (2015) [Ref]

We demonstrate molecular beam epitaxy growth of p-InAs layers on GaAs-buffered GaSb that may be suitable for terahertz applications. GaAs buffer deposition is initiated by applying growth interruption. Reflection high-energy electron diffraction shows that GaAs growth proceeds to a quasi-two-dimensional growth mode. The scheme allows growth of a p-InAs layer 600 nm to 1.0 µm thick. Growth performed without GaAs and growth interruption resulted in decomposition of the p-InAs. When the scheme is used, the ensuing p-InAs first follows quasi-two-dimensional growth before favoring faceted islanding. Under 800-nm-wavelength femtosecond laser excitation, the p-InAs layer generates terahertz signals 70% of that of bulk p-InAs.

Copyright 2015 The Japan Society of Applied Physics


C. P. Sadia, A.M. Laganapan, M.A. Tumanguil, E. Estacio, A. Somintac, A. A. Salvador, C. T. Que, K. Yamamoto, and M. Tani

Journal of Applied Physics 112, 123514 (2012) [PDF] [Ref]

Intense terahertz (THz) electromagnetic wave emission was observed in undoped GaAs thin films deposited on (100) n-GaSb substrates via molecular beam epitaxy. GaAs/n-GaSb heterostructures were found to be viable THz sources having signal amplitude 75% that of bulk p-InAs. The GaAs films were grown by interruption method during the growth initiation and using various metamorphic buffer layers. Reciprocal space maps revealed that the GaAs epilayers are tensile relaxed. Defects at the i-GaAs/n-GaSb interface were confirmed by scanning electron microscope images. Band calculations were performed to infer the depletion region and electric field at the i-GaAs/n-GaSb and the air-GaAs interfaces. However, the resulting band calculations were found to be insufficient to explain the THz emission. The enhanced THz emission is currently attributed to a piezoelectric field induced by incoherent strain and defects.

Copyright 2012 American Institute of Physics

PhD Dissertation

C. P. Sadia. ``Molecular Beam Epitaxy Growth of Gallium Arsenide Films on Gallium Antimonide (100) for Novel Terahertz Emitters". Ph.D. dissertation. University of the Philippines Diliman. July 2016.

Download dissertation defense slides here.

Invention Disclosure

``A semiconductor element with a constricting buffer layer". Link: IPPHL


  • 2016 Invention Disclosure Incentive Award

Links: UP Diliman Invention Disclosure Award Ceremony

UP Diliman News

  • 2013 CHED Republica Award (Outstanding Research Publication Award) Qualifier

International Publication Award by the UP System for the paper ``Intense terahertz emission from molecular beam epitaxy-grown GaAs/GaSb(001)," C. P. Sadia, A.M. Laganapan, M.A. Tumanguil, E. Estacio, A. Somintac, A. A. Salvador, C. T. Que, K. Yamamoto, and M. Tani.

Link: OVPAA page

  • Ph.D. scholarship and research grant from the Commission on Higher Education (CHEd) through the CHEd - National Institute of Physics as a Center of Excellence Program.


Associate Member, National Research Council of the Philippines

General Santos Avenue, Bicutan, 1631 Taguig City, Philippines

Researcher/member, Condensed Matter Physics Laboratory (Semiconductor Research)

National Institute of Physics, College of Science, University of the Philippines Diliman

1101 Quezon City, Philippines

Member, Philippine Association of Physics and Science Instructors (PAPSI)