Growth of thick heavily boron-doped diamond single crystals: Effect of microwave power density

Abstract

The fabrication of diamond-based vertical power devices which are the most suited for high current applications requires the use of thick heavily boron-doped (B-doped) diamond single crystals. Although the growth of thin B-doped diamond films is well controlled over a large concentration range, little is known about the growth conditions leading to heavily doped thick single crystals. In this paper, it was found that the microwave power densities (MWPD) coupled to the plasma used to synthesize B-doped diamond by chemical vapor deposition is one of the key parameters allowing tuning doping efficiencies over two orders of magnitude. At high MWPD (above 100 W cm−3) the boron doping efficiency (DE) is extremely low while further increasing the boron concentration in the gas phase is no use as this leads to plasma instability. On the other hand, when low MWPD are used (<50 W cm−3), DE can be strongly increased but twinning and defects formation hampers the surface morphology. The use of intermediate MWPD densities has been demonstrated as the key in obtaining thick heavily B-doped diamond crystals (>1020 cm−3) with good morphologies.

Development of Crystallographic Texture and In‐Grain Misorientation in CVD‐Produced Single and Polycrystalline Diamond

“…At least one recent study [16] has pointed out that in-grain orientation gradients can vary, significantly, between different grains. Oblique grains, where growth was often terminated by the neighbors, Full Paper [28,29,31,[33][34][35] that both twining and impurity incorporation can have important roles in different growth sectors: and hence can affect growth velocities plus defect evolution of different crystallographic orientations. This can explain gross differences in misorientations between (100) and other grains in polycrystalline diamond films (see Fig.…”

“…[19,[28][29][30][31][32] Many of such defects exist in the HPHT substrate, [33][34][35] and hence may affect the defect evolution of the homo-epitaxially grown diamond thin films. For example, the HPHT substrates typically contain different types of impurities (H, O, and N).…”

“…For example, the HPHT substrates typically contain different types of impurities (H, O, and N). [33][34][35] It is difficult to avoid incorporation of such impurities in CVD-produced diamond layers. An exhaustive range of very interesting literature, [19,[28][29][30][31][32][33][34] including TEM Full Paper (transmission electron microscopy) studies, [28,29,32] exists on the subject of defects in diamond thin films.…”

Growth of thick and heavily boron-doped (113)-oriented CVD diamond films

“…This confirms the previous observation of an improved doping efficiency on (113) as for low-doped samples. Limiting the amount of diborane introduced for reaching a given doping level is an important advantage since this gas promotes soot formation in the reactor hence limiting the maximum reachable growth duration [26]. The fabrication of vertical Schottky diodes relies on the ability to grow thick heavily-doped CVD material.…”

Heavily Boron Doped Diamond Powder: Synthesis and Rietveld Refinement

“…As the concentration of boron increases, the color of diamond changes from blue to black. Various methods of growing diamond films have also made it possible to produce single crystals with a boron content of >10 20 cm −3 in the lattice [6]. The electrical conductivity of BDD is most often used for the manufacture of electrodes and sensors.…”