Muhammad Anwar Ahmad

InN PHOTOCONDUCTORS ON DIFFERENT ORIENTATIONS OF Si SUBSTRATES

We have fabricated photoconductors of indium nitride (InN) grown by radio frequency (RF) sputtering. The InN thin films were deposited on Si(100), Si(110) and Si(111) substrates at room temperature. The Ag/Al contact has been deposited by thermal evaporation in vacuum (10-5Torr) and then annealed under the flowing of the nitrogen gas environment in order to relieve stress and also induce any favorable reactions between metals and the semiconductor. Current–voltage (I–V) measurements after heat treatment at 400°C were carried out for samples in dark and illumination conditions. It was found that Ag/Al formed a good ohmic contact on top of InN. In addition, the characteristics of the contacts were significantly affected by the orientation of substrates.

Catalyst‐free growth and characterization of ZnO nanoscrewdrivers prepared by thermal evaporation

Purpose – The purpose of this paper is to propose a simple physical evaporation route in which catalyst‐free zinc oxide (ZnO) nanoscrewdrivers were deposited on silicon (Si) (111) substrates.Design/methodology/approach – Prior to the deposition, the Si (111) wafer was cut into pieces of 2×2 cm2. Then, the wafers were dipped for 1 min into mixture buffered oxide etchant to remove native oxide. Then, the samples were rinsed in an ultrasonic bath cleaned with boiling acetone, ethanol, and de‐ionized (DI) water for 10 min. Lastly, the wafers were rinsed in 25 ml DI water in stirred and then were blown dry with nitrogen. In this technique, the starting material is high‐purity metallic zinc (Zn) powder (99.99 per cent pure). Following, the Zn films were then annealed under air environment in the furnace at 500°C for 1 h deprived of any catalysts.Findings – These ZnO samples were studied by scanning electron microscopy, high‐resolution X‐ray diffraction (HR‐XRD), and photoluminescence (PL) spectroscopy. Atomic f...

THE STUDY OF Al0.29Ga0.71N-BASED SCHOTTKY PHOTODIODES GROWN ON SILICON BY PLASMA-ASSISTED MOLECULAR BEAM EPITAXY

In this paper, the growth and characterization of epitaxial Al0.29Ga0.71N grown on Si(111) by RF-plasma assisted molecular beam epitaxy (MBE) are described. The Al mole fraction was derived from the HR-XRD symmetric rocking curve (RC) ω/2θ scans of (0002) plane as x = 0.29. PL spectrum of sample has shown sharp and intense band edge emission of GaN without the existence of yellow emission band, showing that it is comparable in crystal quality of the sample when compared with previous reports. From the Raman measurement of as-grown Al0.29Ga0.71N layer on GaN/AlN/Si sample. We found that the dominant E2 (high) phonon mode of GaN appears at 572.7 cm-1. The E2 (high) mode of AlN appears at 656.7 cm-1 and deviates from the standard value of 655 cm-1 for unstrained AlN. Finally, AlGaN Schottky photodiode have been fabricated and analyzed by mean of electrical characterization, using current–voltage (I–V) measurement to evaluate the performance of this device.

FABRICATION OF GaN HOMO-JUNCTION ON Si (111) SUBSTRATE FOR SENSOR APPLICATIONS

In this paper, we investigated growth of GaN pn-homo junction layers on silicon (111) by plasma-assisted molecular beam epitaxy (PA-MBE) system and its application for photo-sensors. Silicon (Si) and magnesium (Mg) were used in this study as n- and p-dopants, respectively. Structural and optical analysis of the GaN homo-junction samples were performed by using reflection high energy electron diffraction (RHEED), X-ray diffraction (XRD), Raman spectroscopy and photoluminescence (PL) to analyze the crystalline quality of the samples. Surprisingly, the Raman analysis has revealed that there is no quenching of the A1 (LO) peak, with the presence of Si- and Mg-dopants in sample. The pn-junctions sample has good optical quality as measured by the PL system. Electrical characterization of the photo-sensors was carried out by using current–voltage (I–V) measurements.

Photoluminescence Characterization of ZnO Thin Films Grown by RF‐ Sputtering

This article presents photoluminescence (PL) characterization of ZnO thin films deposited by radio‐frequency magnetron sputtering method on sapphire and n‐type Si (100) substrates. PL measurements were carried out at room temperature to investigate the energy band gaps and optical quality of the ZnO thin films. In order to draw a specific picture of surface morphology of ZnO thin films, atomic force microscope images were taken. All the results were compared to the results obtained from the bulk ZnO sample. The results revealed that the energy band gap of ZnO thin films grown on n‐type Si (100) is higher than ZnO on sapphire. However, energy band gap of bulk ZnO is higher compared to both ZnO on n‐type Si (100) and sapphire (Al2O3). This is probably due to the crystalline quality because good crystallinity increases the radiation recombination and hence increase the intensity of the NBE emission.

Polarized Infrared Reflectance Study of InGaN Semiconductor

This article presents the polarized infrared (IR) reflectance study of InGaN/GaN/AlN grown on Si (III) substrate by using plasma assisted MBE (Veeco Gen II). Room temperature polarized IR reflectance measurements were performed at an incident angle of 15° by using a Fourier transform infrared. The reflection spectra obtained were then compared with the modelling spectrum data of damped single harmonic oscillator. Good agreement between the measured and calculated spectra has been obtained.

Polarized Infrared Reflectance Studies of Quaternary In0.04Al0.06Ga0.90N

Group III‐nitride has re‐gained considerable interest recently as wide direct band gap semiconductor materials for opto‐electronic and high power devices. The quaternary InAlGaN have great flexibility in tailoring their band gap profile while maintaining their lattice‐matching and structural integrity. In this study, we report for the first time the polarized infrared (IR) reflectance studies of quaternary In0.04Al0.06Ga0.90N by using Fourier transform infrared spectroscopy of Perkin‐Elmer. The quaternary In0.04Al0.06Ga0.90N epilayers was grown on sapphire by molecular beam epitaxy. The polarized IR reflectance spectra obtained at incident angle of 15° were then compared with modeling spectrum of damped harmonic oscillator. Through this study, the transverse and longitudinal optical phonon modes of quaternary In0.04Al0.06Ga0.90N epilayers were obtained.