Ananta R. Acharya

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

The influence of super-atmospheric reactor pressures (2.5‐18.5bar) on the electrical and structural properties of InN epilayers deposited on GaN/sapphire (0001) templates by high-pressure chemical vapor deposition has been studied. The epilayers were analyzed by Raman, x-ray diffraction (XRD), and Fourier transform infrared reflectance spectrometry to determine the structural properties as well as the phonon frequencies, dielectric function, plasma frequency, layer thickness and damping parameters of the epilayers. For the studied process parameter space, best material properties were achieved at a reactor pressure of 12.5bar and a group-V/III ratio of 2500 with a free carrier concentration of 1.5 � 10 18 cm � 3 , a mobility of the bulk InN layer of 270 cm 2 V � 1 s � 1 , and a Raman (E2 high) FWHM value of 10.3cm � 1 . This study shows that the crystalline layer properties—probed by XRD 2h‐x scans—improve with increasing reactor pressure. V C 2012

Observation of NH2 species on tilted InN (011−1) facets

The structural properties and surface bonding configuration of InN layers grown by high-pressure chemical vapor deposition have been characterized using Raman spectroscopy, x-ray diffraction (XRD), and high resolution electron energy loss spectroscopy. The appearance of the A1(TO) mode at 447 cm−1 in unpolarized z(·)z− Raman spectrum indicates distortions in the crystal lattice due to the growth of tilted plane crystallites. A Bragg reflex in the x-ray diffraction spectrum at 2Θ ≈ 33° has been assigned to tilted InN facets in the polycrystalline InN layer. The high resolution electron energy loss spectrum for this InN layer features vibration modes assigned to NH2 species indicating a surface orientation consistent with the crystalline properties observed in Raman spectroscopy and XRD. The appearance of tilted planes is suggested to be due to the effects of high V–III ratio and lattice mismatch on the growth mechanism.

Surface structure and surface kinetics of InN grown by plasma-assisted atomic layer epitaxy: A HREELS study

The surface bonding configuration and kinetics of hydrogen desorption from InN grown by plasma-assisted atomic layer epitaxy have been investigated. High resolution electron energy loss spectra exhibited loss peaks assigned to a Fuchs–Kliewer surface phonon, N-N and N-H surface species. The surface N-N vibrations are attributed to surface defects. The observation of N-H but no In-H surface species suggested N-terminated InN. Isothermal desorption data were best fit by the first-order desorption kinetics with an activation energy of (0.88 ± 0.06) eV and pre-exponential factor of (1.5 ± 0.5) × 105 s−1.