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HL: Fachverband Halbleiterphysik

HL 19: Nitrides: Devices

HL 19.1: Vortrag

Montag, 31. März 2014, 15:00–15:15, POT 151

Comparison of gallium nitride nanorod growth in MBE and MOVPE on nitridated c-plane sapphire — •Julian Stoever, Marc Sauerbrey, Stephan Figge, Jan Ingo Flege, Timo Aschenbrenner, Gerd Kunert, Jens Falta, and Detlef Hommel — Institute of Solid State Physics, University of Bremen, Bremen

Free-standing, nanocrystalline gallium nitride structures on c-plane sapphire substrates were fabricated by metal-organic vapour phase epitaxy (MOVPE) as well as by molecular beam epitaxy (MBE).
Prior to the growth, a substrate nitridation at high temperature and high ammonia flux in MOVPE was carried out to form AlN islands. These nanoislands act as nucleation centers for the rods. The formation process of the islands was investigated in detail by atomic force microscopy and x-ray photoelectron spectroscopy.
Ga-rich conditions, a sufficient silane supply and MOVPE growth temperatures of 1150 ^∘C result in well separated microcolumns. Structures with diameters up to 3 µm and lengths up to 8 µm were fabricated.
On the other hand, nitrogen-rich growth conditions are necessary to achieve columnar growth in MBE. At temperatures of 835 ^∘C, nanorods with diameters of 50 nm and lengths up to 200 nm occur.
Although the same substrate preparation is used, the growth process differs between MOVPE and MBE resulting in different structures. Scanning electron microscopy and micro photoluminescence investigations performed for both types of columns will be presented.