Introduction The semiconductor single-crystal CVD diamond (ob-tained from the gas phase during homoepitaxial deposi-tion) is a wide band gap semiconductor with a gap width of 5.5 eV. CVD diamond has unique characteristics-high mobility of charge carriers, high carrier saturation speed, high electric breakdown field, the greatest thermal conductivity, high radiation and chemical resistance. On a combination of properties the CVD diamond is superior to other wide band gap semiconductors and is considered a promising material for the creation of a new generation of high-power and high-frequency electronic devices. The main difficulty in realization of the potential of CVD diamond as an electronic material is the problem of creating charge carriers inside it. Compared with conventional semiconductors, dopants in diamond have deeper energy levels that significantly impede the activation of the do-pant (the degree of ionization of the dopant at room temperature is less than 1%). Thus, in order to create an acceptable level of conductivity, it is necessary to increase the level of doping, but in case of boron doping this leads to a decrease of carriers (holes) mobility in diamond. To solve the problem of boron doping of CVD diamond, an approach based on delta-doping technology is known. A thin layer of diamond heavily doped with boron (hav-ing a thickness of 1-2 nm and concentration of boron atoms higher than 5×10 20 cm-3) is formed inside an un-doped defect-free diamond of high quality. To achieve high electronic properties (obtaining high hole mobility and conductivity of the layer), it is necessary to realize sharp boundaries between the doped and undoped materials. Recently, this problem has been successfully solved [1, 2]. This report provides an overview of the results of studies on the growth of electronic-quality epitaxial layers of diamond, the production of heavily boron-doped layers and the study of their characteristics. Experiments The novel microwave plasma assisted CVD reactor for growth of nanometric boron delta-doped layers with ultra-sharp interfaces between doped/undoped materials was built in IAPRAS [1]. Fig. 1 shows a schematic of the reactor. The main features of the reactor are: 1) rapid gas switching; 2) laminar gas flow; 3) axial symmetric resonant mode-symmetric discharge; 4) slow growth of diamond 40-100 nm/h. We achieve rapid gas switching from one input gas to another by a home-made electronic switch. The residence time of the reactor is approximately 5 s. In developed reactor the diamond deposition regimes in which one obtains thin doped delta layers with thickness of 1-2 nm with concentrations of boron about 5·10 20 cm-3 were found. Typical parameters of the delta layer under these conditions are given in Fig. 2 for the SS6-1 sample, in which the boron concentration is 4.8·10 20 cm-3 and thickness is 1 nm. Measurement of the boron concentration in the grown samples was carried out by the secondary ion mass spectroscopy (SIMS) method using a time of flight SIMS setup (IONTOF TOF.SIMS-5). T...

We report on building a novel chemical vapor deposition (CVD) reactor for diamond delta‐doping. The main features of our reactor are: a) the use of rapid gas switching system, (b) the reactor design providing the laminar gas flow. These features provide the creation of ultra‐sharp interfaces between doped and undoped material and minimize the prolonged ”tails” formation in the doping profile. It is proved by optical emission spectroscopy that gas switching time is not more than 10 seconds. Using the novel reactor we have grown the nanometer‐thin layers of boron doped diamond. The FWHM of boron concentration profile is about 2 nm which is proved by SIMS. It is shown that the both single delta‐layer and multiple delta‐layers could be grown using the novel CVD reactor. In principle, the reactor could be used for diamond delta doping with other dopants, like nitrogen, phosphorus etc. (© 2016 WILEY‐VCH Verlag GmbH &Co. KGaA, Weinheim)

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The surface morphology of vicinal (100) single-crystal diamond surfaces homoepitaxially grown in a microwave plasma-assisted chemical vapor deposition (MPACVD) reactor is studied. High-pressure and high-temperature (HPHT) single-crystal diamond substrates produced by different vendors are used as substrates. Prior to the CVD growth, substrates were mechanically polished and etched in a separate inductively coupled plasma/reactive ion etching (ICP/RIE) tool using an Ar/Cl 2 gas mixture. The impact of (a) ICP etching regime of the HPHT substrate, (b) substrate polishing, and (c) the HPHT substrate misorientation (off-axis) vicinal angle on the surface morphology is examined. It was found that the ICP etching removes polishing-induced defects in the bulk and also removes diamond particles which are left on the surface of single-crystalline diamond after polishing. The morphology of the surface of the homoepitaxial CVD diamond grown on a substrate, which is free of polishing defects, depends not only on the parameters of the growth process (substrate temperature, composition of the gas mixture, pressure, etc.), but also on the value and direction of the off-axis angle.

The effect of nitrogen addition on the growth rate, quality, and properties of polycrystalline diamond grown by microwave plasma assisted (MPA)CVD is investigated. Two series of experiments are performed at two different microwave power densities (40 and 110 W cm -3 ) using a 2.45 GHz cylindrical microwave reactor. The results show that the beneficial effect of nitrogen is more distinct at higher microwave power densities. To investigate the properties of polycrystalline diamond grown with nitrogen addition, a thick diamond disk of 50 mm diameter is grown with an addition of 50 ppm nitrogen using a 2.45 GHz ellipsoidal microwave reactor. The grown diamond disk has a thermal conductivity of 17.3 W cm -1 K -1 and dielectric loss tangent of 3.7 Â 10 -5 at a frequency of 170 GHz, and its parameters are suitable for application in microwave windows (e.g., gyrotron windows). Our results indicate that it is possible to achieve the increased (by a factor of 2.5) growth rates by nitrogen addition without significant degradation of diamond quality, and properties such as thermal conductivity and dielectric loss tangent.