An antimonide-based InAs/GaSb/InSb short-period superlattice SPSL laser diode on GaSb substrate for mid-infrared emission has been modeled by an accurate eight-band k.p model. By using a realistic graded and asymmetric interface... more
An antimonide-based InAs/GaSb/InSb short-period superlattice SPSL laser diode on GaSb substrate for mid-infrared emission has been modeled by an accurate eight-band k.p model. By using a realistic graded and asymmetric interface profile, calculated energy gap between the electron and heavy-hole miniband shows good agreement with our experimental data. Optical gain and threshold current density are then presented and compared with experimental results of SPSL laser diodes operating in pulsed regime. Analysis of the optical performances obtained at room temperature is made.
E-beam pumped lasers are attractive for Laser Cathode Ray Tubes (LCRT) in projection displays and a variety of applications typically associated with optically pumped lasers. For the first time an InGaN/GaN multiple quantum well (MQW)... more
E-beam pumped lasers are attractive for Laser Cathode Ray Tubes (LCRT) in projection displays and a variety of applications typically associated with optically pumped lasers. For the first time an InGaN/GaN multiple quantum well (MQW) in-plane laser pumped by surface normal pulse and scanning electron beams was demonstrated. Pumping at room temperature (RT) and 80 K showed peak stimulated emission wavelengths of 402 and 409 nm with a full width half maximum (FWHM) of 0.6 nm and 1.2 nm, respectively. The threshold electron beam current densities have been estimated as 60 A/cm 2 for 35 keV electron energy at 80 K using scanning e-beam pumping and 200-300 A/cm 2 at RT using pulsed e-beam pumping with a maximum electron energy of 150 keV. At 80 K, light output of 150 mW was measured out of one facet at an e-beam current of 1.7 mA.
The electronic band structure and optical gain of an InAs/GaSb/InSb short-period superlattice laser diode on a GaSb substrate are numerically investigated with an accurate 8 × 8 k.p model. Using a realistic graded and asymmetric interface... more
The electronic band structure and optical gain of an InAs/GaSb/InSb short-period superlattice laser diode on a GaSb substrate are numerically investigated with an accurate 8 × 8 k.p model. Using a realistic graded and asymmetric interface profile, we obtain a reasonable agreement on band gap energy with our experimental data extracted from laser emissions performed on the laser diode. The optical performance in terms of optical gain is then calculated for the laser structure and we demonstrate the utility of interface design to model short-period superlattice structures.
We report the growth of high indium content InGaN:Yb nanorods grown on c-plane sapphire (0001) substrates using plasma assisted molecular beam epitaxy. The in situ reflection high energy electron diffraction patterns recorded during and... more
We report the growth of high indium content InGaN:Yb nanorods grown on c-plane sapphire (0001) substrates using plasma assisted molecular beam epitaxy. The in situ reflection high energy electron diffraction patterns recorded during and after the growth revealed crystalline nature of the nanorods. The nanorods were examined using electron microscopy and atomic force microscopy. The photoluminescence studies of the nanorods showed the visible emissions. The In composition was calculated from x-ray diffraction, x-ray photoelectron spectroscopy, and the photoluminescence spectroscopy. The In-concentration was obtained from photoluminescence using modified Vegard’s law and found to be around 37% for InGaN and 38% for Yb (561%)-doped InGaN with a bowing parameter b¼1.01eV. The Yb-doped InGaN showed significant enhancement in photoluminescence properties compared to the undoped InGaN. The Yb-doped InGaN nanorods demonstrated the shifting of the photoluminescence band at room temperature, reducing luminescence amplitude temperature dependent fluctuation, and significant narrowing of excitonic emission band as compared to the undoped InGaN. The magnetic properties measured by superconducting quantum interference devices reveals room temperature ferromagnetism, which can be explained by the double exchange mechanism and magnetostriction.
E-beam pumped lasers are attractive for Laser Cathode Ray Tubes (LCRT) in projection displays and a variety of applications typically associated with optically pumped lasers. For the first time an InGaN/GaN multiple quantum well (MQW)... more
E-beam pumped lasers are attractive for Laser Cathode Ray Tubes (LCRT) in projection displays and a variety of applications typically associated with optically pumped lasers. For the first time an InGaN/GaN multiple quantum well (MQW) in-plane laser pumped by surface normal pulse and scanning electron beams was demonstrated. Pumping at room temperature (RT) and 80 K showed peak stimulated emission wavelengths of 402 and 409 nm with a full width half maximum (FWHM) of 0.6 nm and 1.2 nm, respectively. The threshold electron beam current densities have been estimated as 60 A/cm2 for 35 keV electron energy at 80 K using scanning e-beam pumping and 200-300 A/cm2 at RT using pulsed e-beam pumping with a maximum electron energy of 150 keV. At 80 K, light output of 150 mW was measured out of one facet at an e-beam current of 1.7 mA.
The modular multilevel converter (M2C) circuit, a voltage source converter originally introduced to reduce the footprint of high voltage DC systems, is adapted here for a single-phase, low voltage, high power density inverter application... more
The modular multilevel converter (M2C) circuit, a voltage source converter originally introduced to reduce the footprint of high voltage DC systems, is adapted here for a single-phase, low voltage, high power density inverter application (450 VDC, 2 kW, 100 W/in3). The adaptation is achieved by using small, high speed gallium nitride (GaN) transistors in the M2C half-bridge submodules that are stacked in series and parallel to achieve voltage and current requirements. Here the design and analysis of an individual half-bridge cell, and full arm of the M2C topology is presented. To achieve such high power density, factors including gate drive circuit design, submodule electrical performance and thermal management, and the manufacturability of the full arm were considered. This work presents the detailed process of designing and manufacturing the multiple printed circuit boards, as well as thermal and electrical experimental evaluation and analysis. The stringent size and operational requirements drove design iterations between circuit designers and manufacturers.
In this work, room temperature oxidation of GaAs was investigated using ion beam oxidation (mO). In lBO, an ion beam is used to introduce oxygen athermally into the substrate, in this case GaAs. GaAs bonds are broken upon collision with... more
In this work, room temperature oxidation of GaAs was investigated using ion beam oxidation (mO). In lBO, an ion beam is used to introduce oxygen athermally into the substrate, in this case GaAs. GaAs bonds are broken upon collision with the ions, making gallium and arsenic atoms readily available to react with the oxygen species. Ion beam oxidation of GaAs at room temperature was studied as a function ofoxygen ion energy between 500 and is keY. The ion beam oxidized GaAs was characterized in situ by Auger electron spectroscopy (AES) and ex situ with x-ray photoelectron spectroscopy (XPS) for accurate determination of the film chemical composition. Below 1 keY, a thin oxide film is formed: it is composed of Ga20 3 and AS20 3 with almost no metallic arsenic, and presents insulating properties.
As the ion energy increases, preferential sputtering of As and decomposition of AS203 increase and prevent formation of an
insulating film. No damage was detected by Rutherford backscattering spectrometry (RES) combined with ion channeling, in the substrate subjected to IBO below 1 keV.""
E-beam pumped lasers are attractive for Laser Cathode Ray Tubes (LCRT) in projection displays and a variety of applications typically associated with optically pumped lasers. For the first time an InGaN/GaN multiple quantum well (MQW)... more
E-beam pumped lasers are attractive for Laser Cathode Ray Tubes (LCRT) in projection displays and a variety of applications typically associated with optically pumped lasers. For the first time an InGaN/GaN multiple quantum well (MQW) in-plane laser pumped by surface normal pulse and scanning electron beams was demonstrated. Pumping at room temperature (RT) and 80 K showed peak stimulated emission wavelengths of 402 and 409 nm with a full width half maximum (FWHM) of 0.6 nm and 1.2 nm, respectively. The threshold electron beam current densities have been estimated as 60 A/cm2 for 35 keV electron energy at 80 K using scanning e-beam pumping and 200-300 A/cm2 at RT using pulsed e-beam pumping with a maximum electron energy of 150 keV. At 80 K, light output of 150 mW was measured out of one facet at an e-beam current of 1.7 mA.
... at 300 K. The total power input from the ion beam was at all times well below the limit for ion beam heat-ing-From the present description of ÍBO, it can be seen that the main interest of IBO is to allow oxidation at very low 1036... more
... at 300 K. The total power input from the ion beam was at all times well below the limit for ion beam heat-ing-From the present description of ÍBO, it can be seen that the main interest of IBO is to allow oxidation at very low 1036 temperatures. Indeed, oxidation of Si has been ...
ABSTRACT In the present work, we propose and perform extensive simulation study of the novel device structure having a p-GaN back barrier layer inserted in the conventional AlInN/AlN/GaN Gate-Recessed Enhancement-Mode HEMT device for... more
ABSTRACT In the present work, we propose and perform extensive simulation study of the novel device structure having a p-GaN back barrier layer inserted in the conventional AlInN/AlN/GaN Gate-Recessed Enhancement-Mode HEMT device for reducing the short channel effects, gate leakage and enhancing the frequency performance. The influence of the p-GaN back barrier layer on the device performance of the newly proposed structure is done using 2D Sentaurus TCAD simulations. The simulations use Drift–Diffusion (DD) model, Masetti and Canali model, which are calibrated/validated with the previously published experimental results. Simulation are done to analyze the transfer characteristics, transconductance (gm), Gate leakage current (Ig), drain induced barrier lowering (DIBL), subthreshold slope (SS), threshold voltage (Vth), On-current Off-current ratio (Ion/Ioff), gate capacitance (Cgg) and cut off frequency (fT) of the proposed device. A comparison is done between the device without back barrier layer and the proposed device with p-GaN back barrier layer. Use of p-GaN back barrier layer helps to achieve a higher positive Vth due to the depletion effect, reduced Ig, reduced DIBL, prevents degradation of SS and helps to increase the fT. Very impressive fT up to 123 GHz, as compared to 70 GHz for the device without back barrier. These results indicate that AlInN/AlN/GaN Gate-Recessed Enhancement-Mode HEMT structure with p-GaN back barrier is a promising candidate for microwave and switching application.
