arXiv subjects

Shamsul Arafin

Publications and source records attributed to Shamsul Arafin.

5 recordsLinked to original sources

arXiv2026

InGaAs and GaAsSb PIN Nanowire Arrays with Large Absorption around 1.55 μ m for Room Temperature Infrared Applications

We report a comparative analysis between InGaAs and GaAsSb-based top-down cylindrical nanowire arrays fabricated from p-i-n heterostructures. Optical constants measured via spectroscopic ellipsometry were incorporated into FDTD simulations to optimize array geometries. Simulations indicated that GaAsSb nanowire arrays with a diameter of 314 nm and a period of 904 nm achieved a peak absorption of 98% at 1550 nm, while InGaAs nanowire arrays with a 326 nm diameter and 1090 nm period reached 76%. Measurements of fabricated arrays showed absorption of 89% at 1628 nm (GaAsSb) and enhanced sub-bandgap absorption at 1766 nm (InGaAs) at room temperature. These results were confirmed through modelling of the as-fabricated nanowire diameters 330 nm and 411 nm, demonstrating excellent agreement between theory and experiment. In both material platforms, nano-structuring improved the absorption relative to planar films, demonstrating near-unity absorption suitable for practical single-photon detection.

physics.optics↗

arXiv2024

Active Interface Characteristics of Heterogeneously Integrated GaAsSb/Si Photodiodes

There is increased interest in the heterogeneous integration of various compound semiconductors with Si for a variety of electronic and photonic applications. This paper focuses on integrating GaAsSb (with absorption in the C-band at 1550nm) with silicon to fabricate photodiodes, leveraging epitaxial layer transfer (ELT) methods. Two ELT techniques, epitaxial lift-off (ELO) and macro-transfer printing (MTP), are compared for transferring GaAsSb films from InP substrates to Si, forming PIN diodes. Characterization through atomic force microscopy (AFM), and transmission electron microscopy (TEM) exhibits a high-quality, defect-free interface. Current-voltage (IV) measurements and capacitance-voltage (CV) analysis validate the quality and functionality of the heterostructures. Photocurrent measurements at room temperature and 200 K demonstrate the device's photo-response at 1550 nm, highlighting the presence of an active interface.

physics.app-ph↗

arXiv2022

Length Dependence thermal conductivity of Zinc-Selenide (ZnSe) and Zinc Telluride (ZnTe)- A combined first principles and Frequency Domain Thermoreflectance (FDTR) study

In this study, we report the length dependence of thermal conductivity (k) of zinc-blende Zinc-Selenide (ZnSe) and Zinc Telluride (ZnTe) for length scales between 10 nm and 10000 nm using first-principles computations based on density-functional theory. k value of ZnSe is computed to decrease significantly from 11.3 W/mK to 1.75 W/mK as the length scale is diminished from 10 nm to 10 nm. k value of ZnTe is also observed to decrease from 10 W/mK to 1.2 W/mK for the same decrease in length. We also measure the k of bulk ZnSe and ZnTe using Frequency Domain Thermoreflectance (FDTR) technique and observed a good agreement between FDTR measurements and first principles calculations for the bulk ZnSe and ZnTe. Understanding of thermal conductivity reduction at nanometer length scales provides an avenue to incorporate nanostructured ZnSe and ZnTe for thermoelectric applications.

cond-mat.mtrl-sci↗

arXiv2021

Ultrahard BC5 -- an efficient nanoscale heat conductor through dominant contribution of optical phonons

In this work, we study thermal conductivity (k) of BC5, an ultra-hard diamondlike semiconductor material, using first-principles computations and analyze the effect of both isotopic disorder as well as length scale dependence. k of isotopically pure BC5 is computed to be 169 Wm- 1K-1 (along a-axis) at 300K; this high k is found to be due to the high frequencies and phonon group velocities of both acoustic and optical phonons owing to the light atomic mass of Carbon (C) and Boron (B) atoms and strong C-C and B-C bonds. We also observe a dominance of optical phonons (~ 54%) over acoustic phonons in heat conduction at higher temperatures (~500 K). This unusually high contribution of optical phonons is found to be due to a unique effect in BC5 related to a weaker temperature dependence of optical phonon scattering rates relative to acoustic phonons. The effect is explained in terms of high frequencies of optical phonons causing decay into other high frequency phonons, where low phonon populations cause the decay term to become insensitive to temperature. The effect further leads to high nanoscale thermal conductivity of 77 Wm-1K-1 at 100 nm length scale due to optical phonon meanfreepaths being in nanometer regime. These results provide avenues for application of BC5 in nanoscale thermal management.

cond-mat.mtrl-sci↗

arXiv2020

All-MOCVD-Grown Gallium Nitride Diodes with Ultra-Low Resistance Tunnel Junctions

We carefully investigate three important effects including postgrowth activation annealing, delta (δ) dose and p+-GaN layer thickness and experimentally demonstrate their influence on the electrical properties of GaN p-n homojunction diodes with a tunnel junction (TJ)-based p-contact. The p-n diodes and TJ structures were monolithically grown by metalorganic chemical vapor deposition (MOCVD) in a single growth step. By optimizing the annealing time and temperature for magnesium (Mg) activation and introducing δ-doses for both donors and acceptors at TJ interfaces, a significant improvement in electrical properties is achieved. For the continuously-grown, all-MOCVD GaN homojunction TJs, ultra-low forward voltage penalties of 158 mV and 490 mV are obtained at current densities of 20 A/cm2 and 100 A/cm2, respectively. The p-n diode with an engineered TJ shows a record-low normalized differential resistance of 1.6 x 10-4 Ω-cm2 at 5 kA/cm2.

cond-mat.mtrl-sci↗