Asghar Asgari

Bio: Asghar Asgari is an academic researcher from University of Tabriz. The author has contributed to research in topics: Graphene & Quantum dot. The author has an hindex of 17, co-authored 131 publications receiving 1169 citations. Previous affiliations of Asghar Asgari include University of Western Ontario & University of Western Australia.

Effects of partially occupied sub-bands on two-dimensional electron mobility in AlxGa1-xN/GaN heterostructures

Abstract: In this article we present a study of the effect that partial occupancy of sub-bands on the two-dimensional electron mobility at different temperatures, using a fully numerical calculation in unintentionally doped AlxGa1−xN/GaN heterostructures with different Al mole fraction in the AlxGa1−xN barrier. The analysis of our results clearly indicates that the effect of partial sub-band occupancy be considerable, especially at higher temperatures and higher Al mole fractions when more than one sub-band is occupied. Comparison of our calculated results with published experimental data shows good agreement.

Electron mobility, Hall scattering factor, and sheet conductivity in AlGaN/AlN/GaN heterostructures

Abstract: In this paper, we present a study of the effect of temperature on the two-dimensional electron mobility, Hall scattering factor, and sheet conductivity, using a fully numerical calculation in unintentionally doped AlxGa1−xN/AlN/GaN heterostructures. The analysis of our results clearly indicates that the effect of partial sub-band occupancy is considerable, especially at higher operating temperatures when more than one sub-band is occupied. The comparison of our calculated results with published experimental data is shown to be in good agreement.

High performances III-Nitride Quantum Dot infrared photodetector operating at room temperature

Abstract: In this paper we present a novel long wave length infrared quantum dot photodetector. A cubic shaped 6nm GaN quantum dot (QD) within a large 18 nm Al0.2Ga0.8N QD (capping layer) embedded in Al0.8Ga0.2N has been considered as the unit cell of the active layer of the device. Single band effective mass approximation has been applied in order to calculate the QD electronic structure. The temperature dependent behavior of the responsivity and dark current were presented and discussed for different applied electric fields. The capping layer has been proposed to improve upon the dark current of the detector. The proposed device has demonstrated exceptionally low dark current, therefore low noise, and high detectivity. Excellent specific detectivity (D*) up to ~3 × 108CmHz1/ 2/W is achieved at room temperature.

The effects of GaN capping layer thickness on two-dimensional electron mobility in GaN/AlGaN/GaN heterostructures

Abstract: In this paper we present a study of the effect of GaN capping layer thickness on the two-dimensional (2D)-electron mobility and the two-dimensional electron gas (2DEG) sheet density which is formed near the AlGaN barrier/buffer GaN layer. This study is undertaken using a fully numerical calculation for GaN/Al x Ga 1− x N/GaN heterostructures with different Al mole fraction in the Al x Ga 1− x N barrier, and for various values of barrier layer thickness. The results of our analysis clearly indicate that increasing the GaN capping layer thickness leads to a decrease in the 2DEG density. Furthermore, it is found that the room-temperature 2D-electron mobility reaches a maximum value of approximately 1.8×10 3 cm 2 /Vs −1 for GaN capping layer thickness grater than 100 A with an Al 0.32 Ga 0.68 N barrier layer of 200 A thick. In contrast, for same structure, the 2DEG density decreases monotonically with GaN capping layer thickness, and eventually saturates at approximately 6×10 12 cm −2 for capping layer thickness greater than 500 A. A comparison between our calculated results with published experimental data is shown to be in good agreement for GaN capping layers up to 500 A thickness.

Light-emitting diodes

Abstract: Light-Emitting Diodes. (Monographs in Electrical and Electronic Engineering.) By A. A. Bergh and P. J. Dean. Pp. viii+591. (Clarendon: Oxford; Oxford University: London, 1976.) £22.

太阳电池器件物理 = Solar cell device physics

Abstract: There has been an enormous infusion of new ideas in the field of solar cells over the last 15 years; discourse on energy transfer has gotten much richer, and nanostructures and nanomaterials have revolutionized the possibilities for new technological developments. However, solar energy cannot become ubiquitous in the world's power markets unless it can become economically competitive with legacy generation methods such as fossil fuels. The new edition of Dr. Stephen Fonash's definitive text points the way toward greater efficiency and cheaper production by adding coverage of cutting-edge topics in plasmonics, multi-exiton generation processes, nanostructures and nanomaterials such as quantum dots. This book's new structure improves readability by shifting many detailed equations to appendices, and balances the first edition's semiconductor coverage with an emphasis on thin-films. Further, it now demonstrates physical principles with simulations in the well-known AMPS computer code developed by the author. This classic text is now updated with new advances in nanomaterials and thin films that point the way to cheaper, more efficient solar energy production and, many of the detailed equations from the first edition have been shifted to appendices in order to improve readability. It carries important theoretical points are now accompanied by concrete demonstrations via included simulations created with the well-known AMPS computer code.

Changes in the electronic structure and properties of graphene induced by molecular charge-transfer

Abstract: Interaction with electron donor and acceptor molecules such as aniline and nitrobenzene brings about marked changes in the Raman spectrum and the electronic structure of graphene, prepared by the exfoliation of graphitic oxide.