Morphologies and photoluminescence properties of GaN‐based thin films grown on non‐single‐crystalline substrates

Abstract

Morphologies and photoluminescence properties of gallium nitride‐based thin films grown on non‐single‐crystalline substrates were investigated. The films were directly grown on quartz glass and amorphous‐carbon‐coated graphite substrates by a molecular beam epitaxy apparatus which has dual nitrogen plasma cells. Co‐supplying of indium and gallium with simultaneous operation of the dual nitrogen plasma cells brought isolated and nano‐pillar‐shaped structures to the films. On the other hand, such structures were not obtained when the films were grown by the single plasma cell operation. Photoluminescence (PL) properties of the films greatly depended upon the morphologies. The intensities of the PL peaks emitted from the films which have such nano‐pillar shaped structures were quite intense although the peak energies shifted to lower energy sides compared with those of the films grown by the single plasma cell operation.

Properties of GaN-based nanopillar-shaped crystals grown on a multicrystalline Si substrate

“…22 In this study, the nanopillar-shaped crystals are obtained without such buffer layers. Therefore, it can be concluded from the data presented here, as well as from our previous results, 18 that nanopillar-shaped crystals can be obtained regardless of the substrate material and/or the existence of an underlying buffer layer. Impurity doping is necessary to fabricate devices based on the nanopillar-shaped crystals.…”

“…18 Such substrate temperatures are too high for the growth of In-containing group-III nitrides because of the high dissociation pressure of indium nitride (InN). 21 In such conditions, re-evaporation of In occurs during film growth, and as a result the In-contents in the films decreases drastically to about 1%.…”

“…This pronounced re-evaporation process is believed to result in the formation of the nanopillar-shaped crystals observed before. 18 The same growth conditions were applied here to facilitate nanocrystal growth on multicrystalline Si substrates.…”

“…The substrates were heated to 965 • C in a vacuum chamber, the temperature was maintained for 10 min, and then decreased to 900 • C to achieve film growth. Gallium and In (needed to obtain the nanopillar-shaped crystals using this method 18 ) were evaporated from conventional effusion cells at temperatures of 1030 and 930 • C respectively. The fluxes of Ga and In were determined using a beam flux monitor, and were found to be 1.9 and 2.3×10 -6 Torr respectively.…”

“…We have reported that GaN-based nanopillar-shaped crystals can be grown on certain non-single crystalline substrates such as quartz glass and graphite-base substrates. 18 However, there have been no reports on the growth of such nanocrystals on multicrystalline Si substrates. Such substrates permit size upscaling and control of the electrical properties required for device fabrications.…”