No abstract

No abstract

ZnO grown by atomic layer deposition (ALD) is an interesting material for electronic applications requiring low processing temperature. Herein, it is shown that the electrical conductivity of ZnO ALD films can be varied from 10 À1 to 10 2 Ω À1 cm À1 by moving the growth conditions from oxygen rich to zinc rich, through changing the deposition temperature between 100 and 200 C. The temperature-dependent photoluminescence (PL) studies show evidence that shallow defect states in ZnO ALD films are clearly influenced by oxygen-and zincrich conditions, which affect the binding energy of existing donors as well as the relative intensity from donor-to acceptor-related luminescence. The films grown at 100 C, under O-rich conditions, are more resistive and show considerably more intensive acceptor-related PL bands than those grown at 200 C, when Znrich conditions are achieved. Moreover, scaling of electron concentration with the growth temperature is accompanied by a variance of the bandgap due to the Burstein-Moss effect. It is shown that the acceptor-related conductivity of ZnO ALD can be achieved by nitrogen doping under O-rich conditions. The related homojunction with the rectification ratio of 4 Â 10 4 (at AE 2 V) is obtained based on ZnO ALD films deposited at 100 C.

Phone: þ1-807-3438311, Fax: 1 201 839 4341InN thin films were grown by a new technique, migration enhanced afterglow (MEAglow), a chemical vapour deposition (CVD) form of migration enhanced epitaxy (MEE). Here we describe the apparatus used for this form of film deposition, which includes a scalable hollow cathode nitrogen plasma source. Initial film growth results for InN are also presented including atomic force microscopy (AFM) images that indicate step flow growth with samples having root mean square (RMS) surface roughness of as little as 0.103 nm in some circumstances for film growth on sapphire substrates. X-ray diffraction (XRD) results are also provided for samples with a full width half maximum (FWHM) of the (0002) v-2u peak of as little as 290 arcsec. Low pressure conditions that can result in damage to the InN during growth are described.1 Introduction We report on the initial results for indium nitride films grown by a new technique that we have coined migration enhanced afterglow (MEAglow) deposition. Traditionally in RF plasma MBE systems, for the migration enhanced epitaxy (MEE) of group III metal nitrides, the metal is deposited as a thin wetting layer on a substrate and is subsequently nitrided using a nitrogen plasma to form a thin nitride semiconductor layer. A number of cycles of metal deposition with subsequent nitriding are used to build up a thicker film. Past thought has limited the thickness of the metal layer used for each cycle because deposition of more than a couple of monolayers of metal at a time can result in the formation of metal droplets on the substrate surface. It was believed that the nitridation of metal droplets would be difficult at best. However, recently it has been shown that even with these droplets being present good quality InN film growth can be achieved using thick metal deposition in a process that may be similar in some respects to liquid phase epitaxy (LPE) [1].For the work presented here we have migrated these recent MEE results to a low pressure chemical vapour deposition (CVD) environment for the deposition of InN. A nitrogen plasma is also used in this situation, however the