A new method is proposed for the fabrication of thin films consisting of closely packed nm-size metallic grains. The method is based on laser ablation of metallic (Cu) target and cascade fission of ejected liquid metallic drops charged in the laser torch plasma. It is suggested that cascade fission is limited by field emission current from the drop surface, which stops this process sharply when the Cu granule size diminishes down to about 10 nm. The fabricated films, free oxidized in air, are shown to consist of one or several layers of monodisperse spherical Cu grains, 8 nm in diameter, covered by about a 1 nm thick Cu2O layer.

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We report on first demonstration of violet light emitting diodes (LED) based on AlGaN/GaN/AlGaN heterostructures grown by hydride vapor phase epitaxy (HVPE). The unique aspects of this technological approach are (i) growth of Al-containing epitaxial material by HVPE and (ii) use of HVPE to fabricate submicron multi-layer epitaxial structures. The LEDs provide light emission at the wavelength of 415-420 nm that did not shift with forward current. External efficiency up to 2.5% is reached at the current of 20 mA. The brightness of LED lamp is as high as 400-500 mcd. This suggests HVPE as an alternative technique for growing AlGaN-based LED structures. Results of the LED modeling and characterization are discussed.1 Introduction Group-III nitrides are the attractive materials for application in visible and UV optoelectronic and electronic devices. Significant progress in GaN-based technology has been achieved with metal organic chemical vapor deposition (MOCVD). Blue, green and white light emitting diodes (LEDs), violet laser diodes, high electron mobility transistors, and ultra-violet photodiodes have recently been developed [1,2]. Historically, HVPE is one of the first techniques employed for GaN growth [3], which has been successfully used to fabricate thick, high-purity quasi-bulk substrates [4,5]. In addition, HVPE possess other advantages such as ability to (i) combine deposition of thick low-defect layers and thin device multi-layer structures in the same growth run and (ii) easily grow high-quality AlGaN layers in the whole composition range. Moreover, HVPE can provide low-impurity films, as it is a carbon-free process producing free HCl in a reactor, which getters metallic impurities. Thus, HVPE technique can be considered as an alternative cost-effective epitaxy technique for fabrication of AlGaN-based devices.TDI has previously reported on HVPE growth of submicron multi-layer AlGaN-based epitaxial structures for optoelectronic and electronic devices [6]. This paper is aimed at demonstrating the capability of HVPE to fabricate AlGaN/GaN/AlGaN violet LED structures. Optimization of the structure design by modeling and characteristics of the violet LEDs are discussed.

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