Diamond has the highest thermal conductivity of any natural material. It can be used to integrate with GaN to dissipate heat from AlGaN/GaN high electron mobility transistor (HEMT) channels. Much past work has investigated the thermal properties of GaN-on-diamond devices, especially the thermal boundary resistance between the diamond and GaN (TBR_eff,Dia/GaN). However, the effect of SiN_x interlayer structure on the thermal resistance of GaN-on-diamond devices is less investigated. In this work, we explore the role of different interfaces in contributing to the thermal boundary resistance of the GaN-on-diamond layers, specifically using 100 nm layer of SiN_x, 80 nm layer of SiN_x, 100 nm layer of SiN_x with a 20 nm × 20 nm periodic structure. Through combination with time-domain thermoreflectance measurement and microstructural analysis, we were able to determine that a patterning SiN_x interlayer provided the lower thermal boundary resistance (32.2 ± 1.8 m²KGW⁻¹) because of the diamond growth seeding and the diamond nucleation surface. In addition, the patterning of the SiN_x interlayer can effectively improve the interface bonding force and diamond nucleation density and reduce the thermal boundary resistance of the GaN-on-diamond. This enables significant improvement in heat dissipation capability of GaN-on-diamond with respect to GaN wafers.

Due to the outstanding thermal stability of diamond film, diamond films have extensive application prospects in fields such as electronics, optics, biomedicine, and aerospace, and are one of the important materials driving the development of modern science and technology. Moreover, the cost of single-crystal diamond substrates is high, and it is difficult to achieve large-scale batch production. A direct current arc plasma jet chemical vapor deposition method, combined with post-treatment steps such as nano-diamond seed crystal implantation, surface modification, and high-temperature annealing, is used to prepare high-quality diamond films. The relationship between the thermal conductivity and optical properties of diamond films is analyzed in detail. The experimental results showed that diamond film has a relatively smooth surface, with a surface roughness that can reach 3 nm. As the temperature rises, diamond films exhibit good crystal orientation and thermal stability, the FWHM of reflection peaks become smaller, and thermal conductivity can reach 1734 W/(m·K). The infrared testing analysis also confirmed that the diamond film has excellent thermal diffusion properties. When the diamond film is applied to power device chips, it can effectively reduce the junction temperature of 30 °C. The preparation method proposed in this paper is expected to break through the cost and scale limitations of high-performance diamond films, thereby promoting the wide application of diamond films in industries.

Graphene films are widely used in thermal management of electronic devices due to their excellent properties such as high flexibility, high thermal conductivity and light weight. However, in the traditional preparation process, some structural defects are introduced, which will lead to an increase in phonon scattering, thereby reducing the thermal conductivity of graphene. Therefore, a new method for preparing graphene thin films is proposed by using the evaporation method; the graphene oxide composite film is prepared by adding carbon-rich molecules (CRMs) to the graphene oxide dispersion liquid. The experimental results show that the addition of a mass fraction of 0.15% CRMs helps to form continuous strips and channels, which are beneficial to the construction of the internal aromatic structure of graphene and improve the crystallinity of graphene film. The in-plane thermal conductivity of the composite film increased from 598.74 W/(m·K) to 704.27 W/(m·K) after adding carbon-rich molecules. However, excess CRMs can lead to the formation of disordered structures during graphitization, which will reduce the thermal conductivity of the film to a certain extent. The radiation properties of graphene films are also proposed to verify the validity of the above conclusions, and the results show that the graphene film with a mass fraction of 0.24% CRMs has better heat dissipation performance, which can be reduced by 5 °C compared with that of pure graphene film. Through the application of graphene in new energy car seats, it is proved that compared with the resistance wire seats, graphene seats have better performance in terms of a fast heating speed and uniform heating.