Transport characteristics of indium nitride (InN) films grown by plasma assisted molecular beam epitaxy (PAMBE)



We report on the PAMBE-growth of high-quality InN layers with In polarity and on the influence of growth parameters such as Indium-to-nitrogen flux ratio as well as substrate temperature on the electronic transport characteristics of these layers. The flux ratio was changed between 0.94 to 1.18 near stoichiometric conditions and the growth temperature was varied between 400 and 485 °C as measured by calibrated pyrometer temperature. The InN films were grown on metal-organic vapour deposition (MOCVD) GaN templates 3″ in diameter with InN layer thicknesses of 700 nm as determined by spectroscopic ellipsometry (SE). Under In-rich and near stoichiometric growth conditions a minimum surface root mean square roughness of 0.6 nm was achieved. High resolution X-ray diffraction show purely hexagonal phase growth and no evidence for the presence of cubic inclusions. InN layers grown under optimized growth conditions exhibit a narrow (FWHM 20 meV) near band edge low temperature photoluminescence (PL) spectrum with a PL peak energy of 0.67 eV, indicating an InN band gap energy of ≈ 0.7 eV, consistent with the dielectric function spectrum derived from SE measurements. Room temperature van-der-Pauw Hall measurements reveal high electron mobilities up to 1910 cm2/Vs with mean bulk electron concentrations as low as 5 x 1017 /cm3. Furthermore, efficient surface emission of THz radiation has been demonstrated. (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)