Fabrication of GaN/Diamond Heterointerface and Interfacial Chemical Bonding State for Highly Efficient Device Design

Abstract

The direct integration of gallium nitride (GaN) and diamond holds much promise for high‐power devices. However, it is a big challenge to grow GaN on diamond due to the large lattice and thermal‐expansion coefficient mismatch between GaN and diamond. In this work, the fabrication of a GaN/diamond heterointerface is successfully achieved by a surface activated bonding (SAB) method at room temperature. A small compressive stress exists in the GaN/diamond heterointerface, which is significantly smaller than that of the GaN‐on‐diamond structure with a transition layer formed by crystal growth. A 5.3 nm‐thick intermediate layer composed of amorphous carbon and diamond is formed at the as‐bonded heterointerface. Ga and N atoms are distributed in the intermediate layer by diffusion during the bonding process. Both the thickness and the sp2‐bonded carbon ratio of the intermediate layer decrease as the annealing temperature increases, which indicates that the amorphous carbon is directly converted into diamond after annealing. The diamond of the intermediate layer acts as a seed crystal. After annealing at 1000 °C, the thickness of the intermediate layer is decreased to approximately 1.5 nm, where lattice fringes of the diamond (220) plane are observed.

High Thermal Conductivity in Wafer-Scale Cubic Silicon Carbide Crystals

“…Further heterogeneous integration of these high κ thermal management materials with other semiconductors with high TBC is also challenging. 28,29 Here, we report an isotropic high κ exceeding 500 W m − 1 K − 1 at room temperature in a high-purity waferscale free-standing 3C-SiC bulk crystal grown by low-temperature chemical vapor deposition. The measured κ agrees well with the rst-principles predicted intrinsic κ of perfect single-crystal 3C-SiC.…”

“…Single crystal diamond has a larger wafer size, up to 1 inch, but wide-range adoptions are limited by the high cost and di culty in heterogeneous integration with other semiconductors. 19,20,29 Heterogeneous epitaxial growth of single crystal diamond on Si and GaN is challenging. 29 Current chemical vapor deposited (CVD) polycrystalline diamond results in signi cantly reduced and anisotropic κ.…”

“…19,20,29 Heterogeneous epitaxial growth of single crystal diamond on Si and GaN is challenging. 29 Current chemical vapor deposited (CVD) polycrystalline diamond results in signi cantly reduced and anisotropic κ. 32,33 The 3C-SiC wafer reported in this work can reach up to 6-inch in size with an isotropic high κ exceeding 500 W m − 1 K − 1 .…”

DFT-Based Studies on Carbon Adsorption on the wz-GaN Surfaces and the Influence of Point Defects on the Stability of the Diamond–GaN Interfaces

“…The presented reconstruction patterns could be compared with experimental results concerning the fabrication of the GaN/diamond heterointerface via direct bonding. In particular, the energy dispersive spectroscopy (EDS) mapping revealed in the as-bonded GaN/diamond heterointerface fabricated by a surface-activated bonding (SAB) method [23] the presence of an intermediate layer with the C, Ga, O, and N atoms. After annealing in 700 • C and 1000 • C, the thickness of the intermediate layer decreased down to 1.5 nm, and the C atoms diffused into the GaN substrate adjacent to the intermediate layer.…”

“…However, heterogeneous integration of GaN with diamond leading to the GaN-on-diamond architecture is still challenging. Up to now, three kinds of approaches to fabricate the GaN-on-diamond architecture have been demonstrated: (i) diamond growth on GaN [13][14][15][16], (ii) GaN growth on diamond [17][18][19], and (iii) GaNdiamond bonding technology [20][21][22][23]. In the first two approaches, a nucleation layer is formed at the initial stage of growth, resulting in a large number of defects and grain boundaries at the interface, which have a negative impact on the thermal performance of the GaN-on-diamond device due to the poor thermal conductivity [5].…”