Structural And Optical Properties Of Sputtered Nanocrystalline Indium Nitride On Silicon Substrates

The aim of this project is to study the growth and characterization of nanocrystalline indium nitride (InN) on silicon (Si) substrates by means of various non-contact and non-destructive characterization tools. These include the scanning electron microscopy (SEM), energy dispersive X-ray (EDX) analysis, atomic force microscopy (AFM), and X-ray diffraction (XRD) for structural characterization, and Fourier transform infrared (FTIR) spectroscopy, micro-Raman spectroscopy, and photoluminescence (PL) spectroscopy for optical characterization. Initial works on the structural and optical characterization of the nanocrystalline InN grown on anisotropic (110) orientation of sillicon (Si) substrates have been carried out. Studies are, however, focused on optimizing the deposition conditions for growing nanocrystalline InN by radio frequency (RF) sputtering method. All deposited films obtained under different deposition conditions were slightly nitrogen-rich, but increasing the RF power provided more InN compounds in stoichiometric form. XRD results revealed wurtzite nanocrystalline InN films with a (101) preferred growth orientation for all deposited films. The strong PL peak was observed in the energy of 1.9 eV at room temperature. This higher value of the bandgap is due to the Moss–Burstein shift effect

Characterizations of InN Thin Films Grown on Si (110) Substrate by Reactive Sputtering

Indium nitride (InN) thin films were deposited onto Si (110) by reactive sputtering and pure In target at ambient temperature. The effects of the Ar–N2 sputtering gas mixture on the structural properties of the films were investigated by using scanning electron microscope, energy-dispersive X-ray spectroscopy, atomic force microscopy, and X-ray diffraction techniques. The optical properties of InN layers were examined by micro-Raman and Fourier transform infrared (FTIR) reflectance spectroscopy at room temperature. Structural analysis specified nanocrystalline structure with crystal size of 15.87 nm, 16.65 nm, and 41.64nm for InN films grown at N2/Ar ratio of 100/0, 75/25, and 50/50, respectively. The Raman spectra indicates well defined peaks at 578, 583, and 583 cm−1, which correspond to the A1(LO) phonon of the hexagonal InN films grown at gas ratios of 100 : 0, 75 : 25 and 50 : 50 N2 : Ar, respectively. Results of FTIR spectroscopy show the clearly visible TO [E1(TO)] phonon mode of the InN at 479 cm−1 just for film that were deposited at 50 : 50 N2 : Ar. The X-ray diffraction results indicate that the layers consist of InN nanocrystals. The highest intensity of InN (101) peak and the best nanocrystalline InN films can be seen under the deposition condition with N2/Ar gas mixture of 50 : 50

A Comparative Study of BSF Layers for InGaN Single-Junction and Multi-Junction Solar Cells

Abstract The tunability of the InGaN band gap energy over a wide range provides a noble spectral match to sunlight, making it a suitable material for photovoltaic solar cells. The ineffectiveness of single junction solar cell to convert solar full spectrum into electrical energy leads to transparency loss in addition with excess excitation loss. An efficient BSF layer is an essential structural element to attain high efficiency in solar cells. In this work the impact of the BSF layer for InGaN single-junction and multi-junction solar cells is studied using the computational numerical modeling with Silvaco ATLAS simulation technique. The open circuit voltage (Voc) and circuit current density (Jsc) characteristics of the simulated cells and the variation of external quantum efficiency as a function of solar cell structures have been studied. For the optimized cell structure, the maximum Jsc = 14.6 mA/cm2, Voc = 3.087 V, and fill factor (FF) = 88.15% are obtained under AM1.5G illumination, exhibiting a maximum conversion efficiency of 36.1%

Enhancement of deep violet InGaN double quantum wells laser diodes performance characteristics using superlattice last quantum barrier

Abstract The performance characteristics of InGaN double-quantum-well (DQW) laser diodes (LDs) with different last barrier structures are analyzed numerically by Integrated System Engineering Technical Computer Aided Design (ISE TCAD) software. Three different kind of structures for last quantum barrier including doped- GaN, doped- AlGaN and GaN/AlGaN superlattice last barrier are used and compared with conventional GaN last barrier in InGaN-based laser diodes. Replacing the conventional GaN last barrier with p-AlGaN increased hole flowing in the active region and consequently the radiative recombination which results in the enhancement of output power. However it caused increasing the threshold current due electron overflowing. For solving this problem, the last barrier structure altered with GaN/AlGaN superlattice. The simulation indicates that the electrical and optical characteristics of LDs with the superlattice last barrier, like output power, differential quantum efficiency (DQE) and slope efficiency, has significantly improved, besides the threshold current decreased. The enhancement is mainly attributed to the improvement of hole injection and the blocking electron overflowing which are caused by the reduction of polarization charges at the interface between the barrier and well, and electron blocking layer (EBL)