InAlN Films Research Articles

Atmospheric‐pressure MOVPE growth of In‐rich InAlN

AbstractThis paper reports the atmospheric‐pressure MOVPE growth of In‐rich InAlN. All InAlN films prepared here (Al content:0∼ 0.43) do not show phase separation. The incorporation of Al in InAlN is decreased with increasing growth temperature. A decrease in Al content is also observed for films grown at a position farther from the up‐stream end of the susceptor. The marked decrease in the Al content along the gas flow direction seems to be caused by the shortage of TMA supply at the downstream by the parasitic reaction of TMA. A single‐crystalline InAlN film with an Al content of 0‐0.43 is successfully grown by adjusting growth temperature and TMA/(TMI+TMA) molar ratio. FWHM of X‐ray rocking curve for InAlN is increased with increasing Al content. The carrier concentrations in InAlN films are comparable to that in InN (1‐5 × 1019 cm–3). All the single‐crystalline InAlN films with an Al content of 0‐0.3 show a photoluminescence at room temperature. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

MBE growth and characterization of Mg‐doped InGaN and InAlN

AbstractWe report on the growth of high quality Mg‐doped InGaN and InAlN alloys on (0001) sapphire substrates by molecular beam epitaxy. Phase separation does not occur in InxGa1‐xN films with Indium content up to 0.88. Hall measurement shows that a hole concentration of 7.7x1017 cm–3 is achieved on Mg‐doped In0.04Ga0.96N. When x > 0.11, the Hall samples exhibit strong n‐type polarity, whereas p‐type polarity is confirmed by hot probe measurement for all of Mg‐doped InGaN. Ni/Au film is deposited on Mg‐doped InxGa1‐xN as the p contact met al. A contact resistivity as high as 9.95 Ωcm2 is obtained when x = 0.25 while it is only 6.81x10–5 Ωcm2 when x = 0.85. High quality crack‐free InAlN films are also grown on sapphire substrates with AlN/InN quantum‐well buffer layers. When Mg is incorporated near the solid solubility limit, donor defects form and In0.62Al0.38N films show n‐type polarity by Hall measurement, however lower Mg flux yields p‐type polarity. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Optical Properties of Controllable Self-Assembled Lateral Nanostructures on InN, InAlN, and AlN Thin Films

ABSTRACTUtilizing plasma source molecular beam epitaxy (PSMBE), we have grown epitaxial InxAl1-xN films on (0001) sapphire substrates; the indium concentration, x, varied from 0 to 1. The atomic force microscopy of the films reveals characteristic surface patterns of nanometer scale. The feature size distribution is determined by the film composition and thickness. Both absorption and reflection spectra of the films have additional peaks below the fundamental absorption threshold. These peaks cannot be associated with N vacancies or any other known crystal defects and impurities. We attribute the peaks to electron confinement in the hillocks of the lateral structure by the strong electric field of piezoelectric and spontaneous polarization that is characteristic to nitride semiconductor compounds. The calculated values of the electron energy levels are in good agreement with the spectroscopic data; moreover, the electron confinement model explains the observed temperature dependence of the additional peaks. The hillock size control will allow one to control the optical and transport properties of the films.

High‐Density Etching of Group III Nitride Ternary Films

Due to their wide bandgaps and high dielectric constants, group III nitrides have made significant impact on the compound semiconductor community as blue, green, and ultraviolet light emitting diodes and for their potential use in laser structures and high temperature electronics. Processing of these materials, in particular wet and dry etching, has proven to be extremely difficult due to their inert chemical nature. We report electron cyclotron resonance etching of and as a function of temperature, RF power, pressure, and microwave power. Etch conditions were characterized for rate, profile, and sidewall and surface morphology and compared to etch data for GaN, InN, and AlN. Atomic force microscopy was used to quantify root‐mean‐square roughness of the etched surfaces. We observed consistent trends for the InAlN films where the etch rates increased with increasing concentration of In. The trends were less consistent for the InGaN etch rates.

Growth of InxGa1−xN and InxAl1−xN on GaAs metalorganic molecular beam epitaxy

InxGa1−xN (x=0.07–1.0) and InxAl1−xN (x=0.16–1.0) layers were grown on GaAs substrates by metalorganic molecular beam epitaxy. The films display strong n-type conductivity (n≳1020 cm−3) for a wide range of InGaN compositions but only a limited range for InAlN films. The use of a H2 rather than a He carrier gas produces a lower carrier concentration in the as-grown InGaN material. The surface morphology of the ternary layers is improved by the addition of Al to the surface while it is degraded by the addition of Ga. Nonetheless, the InxGa1−xN is single crystal at low Ga concentrations with the lattice mismatch accommodated by a high density of stacking faults and microtwins. The InN layers contain only the cubic phase, while the ternaries contain both cubic and hexagonal phases.