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Diamond exhibits large application potential in the field of power electronics, owing to its excellent and desirable electronic properties. However, the main obstacles to its development originate from the small‐sized single‐crystal wafers and the instability of the electrical conductivity. This work presents a metal‐oxide‐semiconductor field‐effect transistor (MOSFET) on a diamond substrate derived from a five‐inch (110) highly preferred polycrystalline diamond film. The MOSFETs with excellent performance are fabricated by combining an H‐terminated channel and an epitaxially grown boron‐doped layer as the source/drain contacts of the diamond devices. According to the electrical statistical results of ≈110 devices on the polycrystalline diamond substrate, 44% of devices show normally‐off operation with a maximum current density of 400 mA mm−1, while 56% of devices demonstrate normally‐on operation with a maximum current density of 525 mA mm−1. The normally‐off characteristics are more related to the higher amounts of nitrogen concentration than the grain boundaries. The stable boron‐doped source and drain provide a high concentration of holes, which facilitate transport in the surface p‐type channel induced by the H‐termination. The characteristics of the MOSFETs are inspiring for the fabrication of complementary inverter circuits on large diamond wafers. [ABSTRACT FROM AUTHOR]

The cooling behavior of GaN‐on‐diamond substrate can be enhanced by reducing the thermal boundary resistance (TBR), which is mainly determined by the nature of interlayer. Although SiN film is considered as the primary candidate of dielectric layer, it is still needed to be optimized. In order to facilitate the understanding of the influence of dielectric layer on the TBR of GaN‐on‐Diamond substrate, aluminum nitride (AlN), and silicon nitride (SiN) film were compared systematically, both of which are 100 nm. The time‐domain thermoreflectance (TDTR) measurements, adhesion evaluation, and microstructural analysis methods were adopted to analyse these two interlayers. The results show the TBR of SiN interlayer is as low as 38.5 ± 2.4 m2K GW−1, comparing with the value of 56.4 ± 5.5 m2K GW−1 for AlN interlayer. The difference of TBR between these two interlayers is elucidated by the diamond nucleation density, and the adhesion between the diamond film and GaN substrate, both of which are affected by the surface charge and chemical groups of the dielectric layer. [ABSTRACT FROM AUTHOR]

Abstract: Single‐crystal diamonds are successfully synthesized using microwave plasma chemical vapor deposition. A smooth and flat single‐crystal surface is obtained by optimizing the size relationship between the seed substrate and the square hole of the shielding ring. When the sample grows higher than the polycrystalline diamond on the molybdenum holder, the surface becomes uneven. The polarization characteristics of two kinds of chemical vapor deposition (CVD) layers are compared between flat and uneven surfaces. Abnormal high‐order birefringence occurs in both morphologies, which is related to the dislocation density in the CVD layers. The higher the dislocation density of the sample, the more obvious the high‐order anomalous birefringence. High‐pressure high‐temperature seed substrates have obvious defects, such as dislocations, stacking faults, and boundaries of the growth sector, and these defects are mostly distributed at the edge of seed substrates. When the diamond surface demonstrates an edge‐to‐center morphology, the dislocations in the seed substrate, interface‐induced dislocations, and dislocations formed in the growth layer begin to converge toward the central region of the CVD layer, which results in a smaller area of low stress in the center of the CVD layer. High dislocation density causes the crystal to have a mosaic structure and orientation deviation. [ABSTRACT FROM AUTHOR]

For AlN/diamond structure, the crystal quality of diamond substrates is of great importance for the epitaxial growth of AlN. In this paper, c‐axis‐oriented AlN films are deposited on diamond with different crystal quality by radio frequency (RF) reactive magnetron sputtering. The effects of the microstructure of diamond substrates on the orientation of AlN are studied. The results show that the crystal quality of the diamond films greatly affects the growth behavior of AlN. The surface defects of diamond, such as the amorphous phase, will cause the growth direction of AlN to deviate from the c‐axis, resulting in the disorder of grain orientation. Meanwhile, diamond crystal orientation also has influence on the growth of AlN. The (111) oriented grains of diamond are beneficial to the c‐axis growth of AlN. The interface of AlN nucleation and initial growth plays a vital role in final performance of the films, where there is a transition zone from randomly oriented AlN grains to c‐axis‐oriented grains. The suitable diamond substrate can eliminate the transition zone, and can lead to AlN films with high‐degree c‐axis orientation. For the AlN/diamond structure, there is a transition zone from randomly oriented AlN grains to c‐axis‐oriented grains in the interface of AlN nucleation and initial growth. The high crystalline quality and (111) oriented grains of diamond can eliminate the transition zone, which can lead to the strong c‐axis orientation of AlN films. [ABSTRACT FROM AUTHOR]