Thermal Transport across Metal/β-Ga₂O₃ Interfaces

Abstract

In this work, we study the thermal transport at β-Ga2O3/metal interfaces, which play important roles in heat dissipation and as electrical contacts in β-Ga2O3 devices. A theoretical Landauer approach was used to model and elucidate the factors that impact the thermal transport at these interfaces. Experimental measurements using time-domain thermoreflectance (TDTR) provided data for the thermal boundary conductance (TBC) between β-Ga2O3 and a range of metals used to create both Schottky and ohmic electrical contacts. From the modeling and experiments, the relation between the metal cutoff frequency and the corresponding TBC is observed. Moreover, the effect of the metal cutoff frequency on TBC is seen as the most significant factor followed by chemical reactions and defects between the metal and the β-Ga2O3. Among all β-Ga2O3/metal interfaces, for Schottky contacts, Ni/β-Ga2O3 interfaces show the highest TBC, while for ohmic contacts, Cr/β-Ga2O3 interfaces show the highest TBC. While there is a clear correlation between TBC and the phonon cutoff frequency of metal contacts, it is also important to control the chemical reactions and other defects at interfaces to maximize the TBC in this system.

Properties for Thermally Conductive Interfaces with Wide Band Gap Materials

“…Many prior experimental studies have reached the opposite conclusion and reported that vibrational similarity between two materials is an important governor of thermal interface conductance. 14 , 30 − 32 (Reference ( 33 ) is an exception to this trend and reaches conclusions about the effect of vibrational similarity that are similar to the current study.)…”

“…A number of experimental studies have explained experimentally observed trends for G in metal/insulator systems as a consequence of vibrational overlap between the metal and insulator. 14 , 35 , 37…”

“…Many prior experimental studies report how G of various metal/insulator systems vary as the metal is changed. 14 , 18 , 35 , 38 Changing the metal alters not only how vibrationally similar the metal and insulator are but also interfacial bonding 16 , 18 and the phonon irradiance of the metal. 28 The strength of interfacial bonds between a metal and a substrate varies, and weak interfacial bonds lead to low G .…”

“… 11 However, an experimental understanding of G in wide and ultra-wide band gap materials is emerging only now. 12 − 14 …”

Bonding‐Enhanced Interfacial Thermal Transport: Mechanisms, Materials, and Applications

“…The metal/dielectric interfaces widely exist in complementary metal‐oxide semiconductor transistors, [ 84 ] in form of van der Waals force. In the work of Shi et al., [ 85 ] the ITCs at different metal/β‐Ga 2 O 3 interfaces were measured by TDTR. The experimental results were 31.2, 17.4, 82.7, and 81.7 MW m −2 K −1 for Au/β‐Ga 2 O 3 , Ti/β‐Ga 2 O 3 , Ni/β‐Ga 2 O 3 , and Al/β‐Ga 2 O 3 , respectively.…”