Search

Overheating has emerged as a primary challenge constraining the reliability and performance of next-generation high-performance electronics, such as chiplets and (ultra)wide bandgap electronics. Advanced heterogeneous integration not only constitutes a pivotal technique for fabricating these electronics but also offers potential solutions for thermal management. This study presents the integration of high thermal conductivity semiconductors, specifically, 3C-SiC thin films and diamond substrates, through a room-temperature surface-activated bonding technique. Notably, the thermal conductivity of the 3C-SiC films is among the highest for all semiconductor films which can be integrated near room temperature with similar thicknesses. Furthermore, following annealing, the interfaces between 3C-SiC and diamond demonstrate a remarkable enhancement in thermal boundary conductance (TBC), reaching up to approximately 300%, surpassing all other grown and bonded heterointerfaces. This enhancement is attributed to interfacial reactions, specifically the transformation of amorphous silicon into SiC upon interaction with diamond, which is further corroborated by picosecond ultrasonics measurements. Subsequent to annealing at 1100 C, the achieved TBC (150 MW/m2-K) is record-high among all bonded diamond interfaces. Additionally, the visualization of large-area TBC, facilitated by femtosecond laser-based time-domain thermoreflectance measurements, shows the uniformity of the interfaces which are capable of withstanding temperatures as high as 1100 C. Our research marks a significant advancement in the realm of thermally conductive heterogeneous integration, which is promising for enhanced cooling of next-generation electronics.

The direct integration of GaN with Si can boost great potential for low-cost, large-scale, and high-power device applications. However, it is still challengeable to directly grow GaN on Si without using thick strain relief buffer layers due to their large lattice and thermal-expansion-coefficient mismatches. In this work, a GaN/Si heterointerface without any buffer layer is successfully fabricated at room temperature via surface activated bonding (SAB). The residual stress states and interfacial microstructures of GaN/Si heterostructures were systematically investigated through micro-Raman spectroscopy and transmission electron microscopy. Compared to the large compressive stress that existed in GaN layers grown-on-Si by MOCVD, a significantly relaxed and uniform small tensile stress was observed in GaN layers bonded-to-Si by SAB; this is mainly ascribed to the amorphous layer formed at the bonding interface. In addition, the interfacial microstructure and stress states of bonded GaN/Si heterointerfaces was found can be significantly tuned by appropriate thermal annealing. This work moves an important step forward directly integrating GaN to the present Si CMOS technology with high quality thin interfaces, and brings great promises for wafer-scale low-cost fabrication of GaN electronics., Comment: 15 pages, 3 figures

beta-Ga2O3 is a wide bandgap semiconductor with electrical properties better than SiC and GaN which makes it promising for applications of next-generation power devices. However, the thermal conductivity of \b{eta}-Ga2O3 is more than one order of magnitude lower than that of SiC and GaN, resulting in serious thermal management problems that limit device performance and reliability. This work reports selectively transferring of high thermal conductivity 3C-SiC thin film grown on Si to beta-Ga2O3 (001) substrate using surface activated bonding (SAB) technique at room temperature, to attempt extracting the heat from the surface of the devices. A 4.5-nm-thick interfacial crystal defect layer is formed at the as-bonded 3C-SiC/beta-Ga2O3 interface. The thickness of the interfacial crystal defect layer decreases with increasing annealing temperature, which decreases to 1.5 nm after annealing at 1000 C. No voids and unbonded area are observed at the interfaces, even after annealing at temperature as high as 1000 C. The thermal boundary conductance (TBC) of the 1000 C-annealed 3C-SiC/beta-Ga2O3 interface and thermal conductivity of the beta-Ga2O3 substrate was measured by time-domain thermoreflectance (TDTR). The 3C-SiC/beta-Ga2O3 TBC value was determined to be 244 MW/m2-K, which is the highest value ever reported for SiC/Ga2O3 interfaces, due to the high-quality heterointerface. Our works demonstrate that selective transferring of 3C-SiC film to the beta-Ga2O3 substrate is an efficient path to improve heat dissipation of the \b{eta}-Ga2O3 power devices.

High thermal conductivity electronic materials are critical components for high-performance electronic and photonic devices as either active functional materials or thermal management materials. We report an isotropic high thermal conductivity over 500 W m-1K-1 at room temperature in high-quality wafer-scale cubic silicon carbide (3C-SiC) crystals, which is the second highest among large crystals (only surpassed by diamond). Furthermore, the corresponding 3C-SiC thin films are found to have record-high in-plane and cross-plane thermal conductivity, even higher than diamond thin films with equivalent thicknesses. Our results resolve a long-lasting puzzle that the literature values of thermal conductivity for 3C-SiC are perplexingly lower than the structurally more complex 6H-SiC. Further analysis reveals that the observed high thermal conductivity in this work arises from the high purity and high crystal quality of 3C-SiC crystals which excludes the exceptionally strong defect-phonon scatterings in 3C-SiC. Moreover, by integrating 3C-SiC with other semiconductors by epitaxial growth, we show that the measured 3C-SiC-Si TBC is among the highest for semiconductor interfaces. These findings not only provide insights for fundamental phonon transport mechanisms, also suggest that 3C-SiC may constitute an excellent wide-bandgap semiconductor for applications of power electronics as either active components or substrates.