Anisotropic thermal conductivity of AlGaN/GaN superlattices

Abstract

High thermal conductivity is an important parameter for nitride-based power electronic and deep-UV light emitters. Especially in the latter case short period superlattices and multicomponent alloys are used and the knowledge of the thermal properties of the binary compounds is sufficient. In-plane and cross-plane thermal conductivity of AlGaN/GaN superlattices were measured by differential two-wire 3ω method in the temperature range from 147 to 325 K. Samples were grown by metalorganic vapor phase epitaxy; the structure quality and accuracy of superlattice structures preparation were verified by means of HRXRD and transmission electron microscopy. It was observed, that value of thermal conductivities decrease with decreasing period thickness, while temperature dependencies differ from each other—in-plane thermal conductivity decreases, and cross-plane—increases with increasing temperature. Callaway method was used for thermal conductivity calculation; dependence of boundary scattering rate on the phonon wavelength was taken into account. Minimum thermal conductivity was added to calculated values to include the influence of high frequency acoustic phonons and optical phonons on the heat transport. Calculations are in good agreement with experimental results.

Tuning the lattice thermal conductivity of Sb2Te3 by Cr doping: a deep potential molecular dynamics study

“…It is speculated that (Sb 0.83 Cr 0.17 ) 2 Te 3 and (Sb 0.67 Cr 0.33 ) 2 Ta 3 are somewhat equivalent to SbCrTe 3 /Sb 2 Te 3 superlattices, owing to that the Cr elements are doped at specific atomic layer positions in Sb 2 Te 3 . Meanwhile, in the superlattice system, the thermal conductivity perpendicular to the interface increases with the increase of temperature, 57,58 which may explain why the thermal conductivity of Cr-doping Sb 2 Te 3 does not actually exhibit the T −1 dependence.…”

“…Interestingly, this distinct phenomenon often occurs in superlattice systems, such as Bi 2 Te 3 /Sb 2 Te 3 41 and Si/Ge 56 superlattices. It is speculated that (Sb 0.83 Cr 0.17 Meanwhile, in the superlattice system, the thermal conductivity perpendicular to the interface increases with the increase of temperature, 57,58 which may explain why the thermal conductivity of Cr-doping Sb 2 Te 3 does not actually exhibit the T À1 dependence. To investigate further the effect of Cr-doping on the thermal conductivity of Sb 2 Te 3 , we analyzed the bonding characteristics through the electron localization function (ELF), which represents the probability of discovering a second electron with the same spin near the first reference electron.…”

Toward h-BN/GaN Schottky Diodes: Spectroscopic Study on the Electronic Phenomena at the Interface

“…The thickness of the cap was established based on our standard growth procedures. 19 GaN layers were grown at a pressure of 150 mbar and at a temperature of 1045 °C.…”

“…Structures consisted of a 1.5 μm undoped GaN buffer layer, 0.5 μm n-type GaN layers doped with silicon using silane (SiH 4 ) with a dopant concentration level of 5.5 × 10 18 cm –3 , and a capping layer of 20/50/80 nm undoped GaN. The thickness of the cap was established based on our standard growth procedures . GaN layers were grown at a pressure of 150 mbar and at a temperature of 1045 °C.…”

Calculation of Thermal Conductivity of AlGaN/GaN Superlattices

“…In our previous work, [ 22 ] we have reported results of investigations of anisotropic thermal conductivity of AlGaN/GaN SLs. It was measured by differential 3 ω method, while the Callaway model was used for thermal conductivity calculation.…”