Abstract-Epitaxial growth of p-InAs on GaSb with intense terahertz emission under 1.55-μm femtosecond laser excitation

Cyril P. Sadia, Lorenzo P. Lopez Jr., Ramon M.delos Santos, Joselito E. Muldera, Alexander E.De Los Reyes, Mae Agatha C.Tumanguil, Christopher T.Que, Valynn Katrine Mag-usara, Masahiko Tani, Armando S.Somintac,  Elmer S.Estacio, Arnel A.Salvador,

https://www.sciencedirect.com/science/article/pii/S0040609017309276

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.

Abstract-Porosity dependence of terahertz emission of porous silicon investigated using reflection geometry terahertz time-domain spectroscopy

• Arvin I. Mabilangan¹, 
• Lorenzo P. Lopez Jr.², 
• Maria Angela B. Faustino², 
• Joselito E. Muldera¹, 
• Neil Irvin F. Cabello^1, , , 
• Elmer S. Estacio^1, 2, 
• Arnel A. Salvador^1, 2, 
• Armando S. Somintac^1, 2

• ¹ Condensed Matter Physics Laboratory, National Institute of Physics, University of the Philippines, Diliman 1101, Quezon City, Philippines
• ² Materials Science and Engineering Program, University of the Philippines, Diliman 1101, Quezon City, Philippines
• http://www.sciencedirect.com/science/article/pii/S0749603616312629
• 
  

Porosity dependent terahertz emission of porous silicon (PSi) was studied. The PSi samples were fabricated via electrochemical etching of boron-doped (100) silicon in a solution containing 48% hydrofluoric acid, deionized water and absolute ethanol in a 1:3:4 volumetric ratio. The porosity was controlled by varying the supplied anodic current for each sample. The samples were then optically characterized via normal incidence reflectance spectroscopy to obtain values for their respective refractive indices and porosities. Absorbance of each sample was also computed using the data from its respective reflectance spectrum. Terahertz emission of each sample was acquired through terahertz - time domain spectroscopy. A decreasing trend in the THz signal power was observed as the porosity of each PSi was increased. This was caused by the decrease in the absorption strength as the silicon crystallite size in the PSi was minimized.