Characterization of high quality InN grown on production-style plasma assisted molecular beam epitaxy system

Abstract

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.

Effect of reactor pressure on the electrical and structural properties of InN epilayers grown by high-pressure chemical vapor deposition

“…These values for the bulk free carrier concentration are still higher compared to recently reported bulk free carrier concentrations of 5.6 Â 10 17 cm À3 in InN epilayers grown on GaN by plasma assisted molecular beam epitaxy. 20 Figure 6 depicts the variation of free carrier concentration in the nucleation layer as a function of the reactor pressure, indicating a slight reduction of free carrier concentration with the increasing reactor pressure. This result suggests that the reactor pressure does not significantly alter the nucleation process-and with it the free carrier concentration in the nucleation layer.…”

X-Ray Diffraction and Photoluminescence Studies of InN Grown by Plasma-Assisted Molecular Beam Epitaxy with Low Free-Carrier Concentration

“…Deviations seen in the InN (0002) diffraction angles are attributed to stress due to the different growth conditions used, as described in Ref. 13. Strains are determined from e a = (a -a 0 )/a 0 and e c = (c -c 0 )/c 0 using measured a and c lattice constants and published a 0 = 3.538 Å and c 0 = 5.703 Å of relaxed InN.…”

“…More details may be found in Ref. 13. InN was characterized using x-ray diffraction (XRD), PL spectroscopy, Raman scattering, and the free-carrier concentrations determined by roomtemperature (RT) Hall measurements.…”