Analytical model for 2DEG charge density in β-(AlxGa1-x)2O3/Ga2O3 HFET

In this paper, a physics-based analytical model for Two-Dimensional Electron Gas (2DEG) charge density (ns) and pinch-off voltage (Voff) in β-(AlxGa1-x)2O3/Ga2O3 Heterostructure Field Effect Transistor (HFET) is reported. The modeling approach includes solving the Poisson-Schrödinger equation in β-(AlxGa1-x)O3 barrier layer followed by using standard Fermi-Dirac statistics equations for calculating 2DEG charge density in the potential well. The developed model is then used to analyze the effect of Al composition (x) and barrier thickness (d) of β-(AlxGa1-x)2O3 layer on 2DEG charge density. The obtained parameters from our model for charge density and pinch-off voltages are validated with the experimental results in the literature demonstrating a good accuracy. It was observed that the 2DEG charge density increases with Al composition and AlxGa1-xO barrier layer thickness, but at the cost of increased pinch-off voltage. A trade-off between both is necessary to achieve parametric optimization of β-(AlxGa1-x)2O3/Ga2O3 HFET. This model will be useful to study the various parametric constraints for device optimization in terms of 2DEG charge density and pinch-off voltage.

Экситонная люминесценция двойных монослоев CdTe в матрице ZnTe

A series of ZnTe matrix containing two CdTe monolayers separated by barrier layers of different thicknesses is studied. The dependences of the energies of the exciton emission bands related to the CdTe monolayers, their relative intensities, and temperature behavior on the thickness of the ZnTe barrier layer are determined. It is established that CdTe monolayers can be considered independent of each other with a barrier layer thickness of more than 30 monolayers.

Performance Enhancement of AlGaN/GaN HEMT by Optimization of Device Parameters Considering Nanometer Barrier Layer Thickness

The two-dimensional electron gas (2DEG) at the heterointerface of AlGaN and GaN is a complicated transcendental function of gate voltage, so an analytical charge control model for AlGaN/GaN high electron mobility transistor (HEMT) is presented accounting for all the three regions of operation (i.e., sub-threshold, moderate, and strong-inversion region). In addition to it, the performance of AlGaN/GaN HEMT is highly dependent on the device geometry. Therefore, to get the optimum performance of the device it is advisable to optimize the parameters governing the device geometry. Accordingly, the output and transfer characteristics, threshold voltage, ON current, OFF current, and transconductance are calculated using numerical computations. The present design is tested to calculate the voltage transfer characteristics (VTC) and transient characteristics of the invertor circuit, after the optimization of the device parameters.

Cu(I/II) Metal–Organic Frameworks Incorporated Nanofiltration Membranes for Organic Solvent Separation

Copper-based metal–organic frameworks (MOFs) with different oxidation states and near-uniform particle sizes have been successfully synthesized. Mixed-matrix polyimide membranes incorporating 0.1–7 wt% of Cu(II) benzene-1,2,5-tricarboxylic acid (Cu(II)BTC), Cu(I/II)BTC and Cu(I) 1,2-ethanedisulfonic acid (EDS) (Cu(I)EDS) MOFs were fabricated via non-solvent-induced phase inversion process. These membranes are found to be solvent resistant and mechanically stable. Liquid phase nanofiltration experiments were performed to separate toluene from n-heptane at room temperature. These membranes demonstrate preferential adsorption and permeation of the aromatic toluene over aliphatic n-heptane. The amount of MOF particles incorporated, the oxidation state of the Cu ion and membrane, and barrier layer thickness have a significant impact on the separation factor. Toluene/heptane separation factor at 1.47, 1.67 and 1.79 can be obtained for membranes incorporating 7 wt% Cu(II)BTC, Cu(I/II)BTC and Cu(I)EDS respectively at room temperature.

Seasonal and interannual variabilities of the barrier layer thickness in the tropical Indian Ocean

The seasonal and interannual variations of the barrier layer thickness (BLT) in the tropical Indian Ocean (TIO) is investigated in this study using the Simple Ocean Data Assimilation version 3 (SODA v3) ocean reanalysis dataset. Analysis of this study suggests energetic but divergent seasonal variabilities of BLT in the western TIO (5∘ N–12∘ S, 55–75∘ E) and the eastern TIO (5∘ N–12∘ S, 85–100∘ E). For instance, the thicker barrier layer (BL) is observed in the western TIO during boreal winter as a result of decreasing sea surface salinity (SSS) and deeper thermocline, which are associated with the intrusion of freshwater flux and the weakened upwelling, respectively. On the contrary, the variation of BLT in the eastern TIO mainly corresponds to the variation in thermocline depth in all seasons. The interannual variability of BLT with the Indian Ocean Dipole (IOD) and El Niño–Southern Oscillation (ENSO) is explored. During the mature phase of positive IOD events, a thinner BL in the eastern TIO is attributed to the shallower thermocline, while a thicker BL appears in the western TIO due to deeper thermocline and fresher surface water. During negative IOD events, the thicker BL only occurs in the eastern TIO, corresponding to the deeper thermocline. During ENSO events, prominent BLT patterns are observed in the western TIO corresponding to two different physical processes during the developing and decaying phase of El Niño events. During the developing phase of El Niño events, the thicker BL in the western TIO is associated with deepening thermocline induced by the westward Rossby wave. During the decaying phase of El Niño events, the thermocline is weakly deepening, while the BLT reaches its maxima induced by the decreasing SSS.

Влияние параметров короткопериодной сверхрешетки InGaAs/InGaAlAs на эффективность фотолюминесценции

The results of the study of heterostructures based on short-period InGaAs/InGaAlAs superlattices fabricated by molecular beam epitaxy on an InP substrate with the aim of using them as active regions for vertical-cavity surface emitting lasers of the 1.3 μm spectral range are studied. Photoluminescence and X-ray diffraction studies of the fabricated heterostructures are carried out. It was shown that a change in the ratio of the quantum well thickness and the barrier layer thickness of the superlattice allows one to controllably shift the position of the photoluminescence peak and to provide the heterostructure parameters necessary to achieve lasing at a wavelength of 1.3 μm, while the photoluminescence efficiency remains practically unchanged.