Selective Growth Approach Research Articles

Schottky barrier diode fabricated on oxygen-terminated diamond using a selective growth approach

A Schottky barrier diode (SBD) fabricated on oxygen-terminated diamond using a selective growth approach is demonstrated. Patterned tungsten (W) film was used as the mask, and ohmic contact was formed between W and diamond during the selective growth process. After growth, the selective epitaxial diamond surface was treated by UV-ozone to achieve oxygen termination. Then, Zr/Ni/Au Schottky electrode was patterned on the selective grown diamond surface. The I-V characteristics indicate that the SBD is p-type, and a rectification ratio of more than 5 orders of magnitude at ±20 V at room temperature is observed. The acceptor might be introduced by W incorporated into diamond during selective growth process, and its concentration was determined to be 2.7 × 1014 cm−3 from C−2-V curve. The reverse breakdown voltage of the SBD is 1316 V, corresponding to a breakdown electrical field of 6.3 MV/cm. The reverse current-voltage characteristics show that the UV ozone treatment can favorably suppress reverse leakage current.

Effect of ambient pressure on the selective growth of square In2O3 nanowires

Single crystalline indium oxide (In2O3) nanowires (NWs), formed via a simple vapor transport route, were synthesized by a selective growth approach on patterned SiO2/Si substrates. The selective growth approach enabled us to have a more systematic analysis of the effects of the synthesizing parameters on the growth of the NWs. In this study, the ambient pressure in the quartz tube was controlled in the range of 250–1,000 mTorr, and the dependence of NW size and density was investigated. Statistical analyses demonstrate that the ambient pressure plays an important role in determining the nucleation and crystal growth of In2O3 NWs, thereby affects the diameter, length, and density of the NWs. Our result indicates that the interplay between the source export and the absorption import as well as the coalescence of catalyst droplets are mainly affected by ambient pressure in the quartz tube, which eventually contributes to the yield of NWs on catalytic substrates.

Selective growth of carbon nanotube for via interconnects by oxidation and selective reduction of catalyst

We propose a selective growth approach of carbon nanotubes (CNTs) to prevent interface rupture in CNT via interconnects. Oxidation of the Ni catalyst layer is carried out before via hole patterning and the open hole area of the Ni layer is reduced by annealing in H2 ambient after via hole patterning. It is found that the present scheme provides robust selective growth of CNTs in the via hole and effectively prohibits the interface rupture due to the diffusion of carbon source into the Ni catalyst layer buried under the insulator.

GaN nanostructures and HFET structures selectively grown on silicon substrates by ammonia-MBE

Silicon substrate can be used as a highly effective pseudomask to perform selective growth of GaN by ammonia molecular beam epitaxy (MBE). This can be exploited to fabricate novel photonic and electronic device structures on Si substrates. Growth of GaN micro-pyramids as templates for fabricating InGaN quantum dots, and growth of AlGaN/GaN HFET mesa patterns using the selective growth approach is reported. The facet growth characteristics of the selectively grown GaN micro-pyramids are investigated. μ-photoluminescence (μ-PL) measurements resolving emissions from InGaN quantum dots and/or wells on a single GaN pyramid have been performed, but have found no evidence of formation of InGaN single quantum dot at the apex of the GaN pyramid. Possible improved growth approaches for achieving such single quantum dot structures are discussed. Success in selective growth of the HFET mesa pattern and especially the insulating carbon-doped GaN buffer layer is achieved, demonstrating a promising approach for potential integration of nitride devices with silicon circuits.