We have demonstrated step‐flow growth mode of InN, with monolayer height terrace steps (0.281 nm), using a production‐style PA‐MBE system, GEN200®. The surface morphology exhibits the step‐flow features on relatively large areas and the RMS roughness over an area of 5 × 5 μm2 is 1.4 nm. We also investigated the consequences of In droplets formation during the growth and we have found that the vapor‐liquid‐solid growth mechanism generates defective layer areas underneath droplets that have been formed early in the growth process. The Hall mobility of 1µm thick InN layers, grown in such step‐flow mode is slightly higher than 1400 cm2/Vs while for other growth conditions we have obtained mobility as high as 1904 cm2/Vs at room temperature. The samples exhibit high intensity photoluminescence spectra with a band edge that shifts with free‐carrier concentration. For the lowest carrier concentration of 5.6 × 1017 cm‐3 we observe PL emission at ∼0.64 eV. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Laterally enlarged single crystal diamond is grown on (001) diamond substrates by microwave plasma chemical vapor deposition. Based on the largest side-to-side width of the seed of 7.5 mm, we achieve the as-grown epilayer with the width of about 10 mm between the same two sides. The luminescence difference between the broadened part of the single crystal diamond and the vertically epitaxial part is investigated by characterizing the vertical cross section of the sample, and the possible growth mechanism is suggested. Vertical epitaxy on the top (001) surface and lateral growth on the side surfaces occur simultaneously, and thus the growth fronts along the two directions adjoin and form a coalescence zone extending from the edge of the substrate towards the edge of the expanded single crystal diamond top surface. The luminescence intensity of the nitrogen-vacancy center is relatively high in the coalescence zone and a laterally grown part right below, which are attributed mainly to the higher growth rate. However, stress change and crystal quality change are negligible near the coalescence zone.

We report the simultaneous enlarged growth of seven single crystal diamond (SCD) plates free from polycrystalline diamond (PCD) rim by using a microwave plasma chemical vapor deposition (MPCVD) system. Optical microscope and atomic force microscope (AFM) show the typical step-bunching SCD morphology at the center, edge, and corner of the samples. The most aggressively expanding sample shows a top surface area three times of that of the substrate. The effective surface expanding is attributed to the utilization of the diamond substrates with (001) side surfaces, the spacial isolation of them to allow the sample surface expanding, and the adoption of the reported pocket holder. Nearly constant temperature of the diamond surfaces is maintained during growth by only decreasing the sample height, and thus all the other growth parameters can be kept unchanged to achieve high quality SCDs. The SCDs have little stress as shown by the Raman spectra. The full width at half maximum (FWHM) data of both the Raman characteristic peak and (004) x-ray rocking curve of the samples are at the same level as those of the standard CVD SCD from Element Six Ltd. The nonuniformity of the sample thickness or growth rate is observed, and photoluminescence spectra show that the nitrogen impurity increases with increasing growth rate. It is found that the reduction of the methane ratio in the sources gas flow from 5% to 3% leads to decrease of the vertical growth rate and increase of the lateral growth rate. This is beneficial to expand the top surface and improve the thickness uniformity of the samples. At last, the convenience of the growth method transferring to massive production has also been demonstrated by the successful simultaneous enlarged growth of 14 SCD samples.

In this work, the authors report step-flow growth mode of InN on [0001] oriented GaN templates, using a production-style molecular beam epitaxy system, Veeco GEN200®, equipped with a plasma source. Using adaptive growth conditions, they have obtained a surface morphology that exhibits the step-flow features. The root mean squared roughness over an area of 5×5μm2 is 1.4nm with monolayer height terrace steps (0.281nm), based on atomic force microscopy. It has been found that the presence of In droplets leads to defective surface morphology. From x-ray diffraction, they estimate edge and screw dislocation densities. The former is dominant over the latter. Micro-Raman spectra reveal narrow E22 phonon lines consistent with excellent crystalline quality of the epitaxial layers. The Hall mobility of 1μm thick InN layers, grown in step-flow mode, is slightly higher than 1400cm2∕Vs, while for other growth conditions yielding a smooth surface with no well-defined steps, mobility as high as 1904cm2∕Vs at room temperature has been measured. The samples exhibit high intensity photoluminescence (PL) with a corresponding band edge that shifts with free carrier concentration. For the lowest carrier concentration of 5.6×1017cm−3, they observe PL emission at ∼0.64eV.

Epitaxial growth of InAlGaN/GaN structures are performed on the 𝑐-plane sapphire by pulsed metal organic chemical vapor deposition with different triethylgallium (TEGa) flows in the growth process of InAlGaN quaternary alloys. X-ray photoelectron spectroscopy results show that the Al/In ratio of the samples increases as the TEGa flows increase in the InAlGaN quaternary growth process. High-resolution x-ray diffraction results show that the crystal quality is improved with increasing TEGa flows. Morphology of the InAlGaN/GaN heterostructures is characterized by an atomic force microscopy, and the growth mode of the InAlGaN quaternary shows a 2D island growth mode. The minimum surface roughness is 0.20 nm with the TEGa flows equaling to 3.6 𝜇mol/min in rms. Hall effect measurement results show that the highest electron mobility 𝜇 is 1005.49 cm 2 /Vs and the maximal two-dimensional electron gas is 1.63 × 10 13 cm −2 .