Comment on “Investigation on Anomalous Thermal Quenching of Mn4+ Luminescence in A2XF6:Mn4+” [ECS J. Solid State Sci. Technol. 10 076007 (2021)]

Adachi (ECS J. Solid State Sci. Technol.,10, 076007(2021)) reported that an anomalous enhancement of integrated intensity of Mn4+ luminescence (IPL) in A2XF6:Mn4+ phosphors with increasing lattice temperature was an intrinsic property of the phosphors due to the increased phonon number that makes it possible to gain the parity and spin-forbidden 2Eg → 4A2g transitions.I argue in this comment that it seems still unconvincing to ascribe the anomalous increase of IPL with temperature as an intrinsic property of Mn4+-doped fluorides. Since theoretical derivations of the formulas expressing temperature dependence of the intensities were based on an unjustified assumption.

About the Definition of the Local Equilibrium Lattice Temperature in Suspended Monolayer Graphene

The definition of temperature in non-equilibrium situations is among the most controversial questions in thermodynamics and statistical physics. In this paper, by considering two numerical experiments simulating charge and phonon transport in graphene, two different definitions of local lattice temperature are investigated: one based on the properties of the phonon–phonon collision operator, and the other based on energy Lagrange multipliers. The results indicate that the first one can be interpreted as a measure of how fast the system is trying to approach the local equilibrium, while the second one as the local equilibrium lattice temperature. We also provide the explicit expression of the macroscopic entropy density for the system of phonons, by which we theoretically explain the approach of the system toward equilibrium and characterize the nature of the equilibria, in the spatially homogeneous case.

Analytical study of effect of energy band parameters and lattice temperature on conduction band offset in AlN/Ga2O3 HEMT

Apart from other factors, band alignment led conduction band offset (CBO) largely affects the two dimensional electron gas (2DEG) density ns in wide bandgap semiconductor based high electron mobility transistors (HEMTs). In the context of assessing various performance metrics of HEMTs, rational estimation of CBO and maximum achievable 2DEG density is critical. Here, we present an analytical study on the effect of different energy band parameters-energy bandgap and electron affinity of heterostructure constituents, and lattice temperature on CBO and estimated 2DEG density in quantum triangular-well. It is found that at thermal equilibrium, ns increases linearly with ?EC at a fixed Schottky barrier potential, but decreases linearly with increasing gate-metal work function even at fixed ?EC, due to increased Schottky barrier heights. Furthermore, it is also observed that poor thermal conductivity led to higher lattice temperature which results in lower energy bandgap, and hence affects ?EC and ns at higher output currents.

Эффект саморазогрева в беспереходных вертикальных полевых транзисторах на основе структур "кремний на изоляторе" с различной формой базы

In this work it is simulated the self-heating effect in nanoscale Silicon on Insulator Junctionless FinFET transistor with fin cross section in rectangular, trapeze and triangle form. It is shown that for considered transistor structure the lattice temperature in the middle of the channel is lower than at lateral sides, near source and drain. Besides it at the same conditions the lattice temperature depends on shape of channel cross section too.

Thermal Analysis and Operational Characteristics of an AlGaN/GaN High Electron Mobility Transistor with Copper-Filled Structures: A Simulation Study

In this study, we investigated the operational characteristics of AlGaN/GaN high electron mobility transistors (HEMTs) by applying the copper-filled trench and via structures for improved heat dissipation. Therefore, we used a basic T-gate HEMT device to construct the thermal structures. To identify the heat flow across the device structure, a thermal conductivity model and the heat transfer properties corresponding to the GaN, SiC, and Cu materials were applied. Initially, we simulated the direct current (DC) characteristics of a basic GaN on SiC HEMT to confirm the self-heating effect on AlGaN/GaN HEMT. Then, to verify the heat sink effect of the copper-filled thermal structures, we compared the DC characteristics such as the threshold voltage, transconductance, saturation current, and breakdown voltage. Finally, we estimated and compared the lattice temperature of a two-dimensional electron gas channel, the vertical lattice temperature near the drain-side gate head edge, and the transient thermal analysis for the copper-filled thermal trench and via structures. Through this study, we could optimize the operational characteristics of the device by applying an effective heat dissipation structure to the AlGaN/GaN HEMT.