Abstract
In this report, self-organized GaN nanodots have been grown on Si (111) by droplet epitaxy method, and their density can be controlled from 1.1 × 1010 to 1.1 × 1011 cm-2 by various growth parameters, such as substrate temperatures for Ga droplet formation, the pre-nitridation treatment of Si substrate, the nitridation duration for GaN crystallization, and in situ annealing after GaN formation. Based on the characterization of in situ RHEED, we can observe the surface condition of Si and the formation of GaN nanodots on Si. The surface nitridaiton treatment at 600°C provides a-SiNx layer which makes higher density of GaN nanodots. Crystal GaN nanodots can be observed by the HRTEM. The surface composition of GaN nanodots can be analyzed by SPEM and μ-XPS with a synchrotron x-ray source. We can find GaN nanodots form by droplet epitaxy and then in situ annealing make higher-degree nitridation of GaN nanodots.
Highlights
Group-III nitride based semiconductors have been successful commercialized as light emitting diodes (LED) and high electron mobility transistors (HEMT) [1,2]
We focused on the characterization of gallium nitride (GaN) nanodots by scanning photoemission microscopy (SPEM) and x-ray photoelectron spectroscopy (XPS) from a synchrotron radiation x-ray source
In order to obtain higher density of GaN nanodots on Si for future applications, we investigated the density of GaN nanodots by controlling the substrate temperatures, nitridation time for GaN crystallization, the pre-nitridation treatment of substrates, and in situ annealing after GaN nanodot formation from the images of field emission scanning electron microscopy (FESEM)
Summary
Group-III nitride based semiconductors have been successful commercialized as light emitting diodes (LED) and high electron mobility transistors (HEMT) [1,2]. An enormous interest in gallium nitride (GaN) nanostructures can be observed due to their strong carrier confinement phenomenon. GaN quantum dots (QDs) are highly potential materials for the applications in electronics such as single electron transistors, and in optoelectronics such as QD lasers, single photon source and photodetectors [3,4]. High-density GaN nanodots and nanorods are expected to be illuminated working electrodes of photoelectrochemical water splitting to generate hydrogen gas. The hydrogen evolution by natural energy will be an important technique to prevent the global warming in the future [5]. For the fabrication of self-assembled semiconductor nanostructures, several methods were proposed so far
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