Search for content and authors
 

Effect of carrier gas on the optical and structural properties of GaN

Evgenia Gridneva 1Eberhard Richter 1Martin Feneberg 2Markus Weyers 1Günther Tränkle 1

1. Ferdinand-Braun-Institut für Höchstfrequenztechnik (FBH), Gustav-Kirchhoff-Str. 4, Berlin 12489, Germany
2. Otto-von-Guericke-Universität Magdeburg, Institut für Experimentelle Physik, Universitätsplatz 2, Magdeburg 39106, Germany

Abstract

Hydride vapor phase epitaxy (HVPE) is a promising technique and being actively developed for growth of GaN substrates which are demanded for fabrication of e.g. light emitting diodes and laser diodes in the short wavelength range. The main reaction providing GaN growth in HVPE is that of ammonia and gaseous GaCl, with hydrogen and nitrogen being the usual carrier gases. We have studied the impact of carrier gas composition using mixtures of H2 and N2 on the growth process. Experiments were carried out in AIXTRON vertical HVPE reactor using 3.5 µm GaN substrates grown on sapphire templates by MOVPE (metal-organic vapor phase epitaxy). In-situ reflectometry, Nomarski microscopy, photoluminescence and X-ray diffraction were used to characterize the grown layers. After readjusting NH3 and GaCl partial pressures according to the simulated gas-flow dynamics, a H2 fraction in the range of 0-60 % was found to be favorable regarding the layer quality. Under these conditions it was possible to grow 100 µm thick GaN films without cracks and at a high growth rate of about 240-300 µm/h. X-ray diffraction measurements of 002 and 302 rocking curves on 100 µm thick films revealed dislocations densities of 108 cm-2. 70% of H2 resulted in cracks and damaged film surface, possibly due to enhanced GaN decomposition, which would also explain the decreased growth rate of only around 150 µm/h. Broadened X-ray rocking curves indicated a higher dislocation density of about 7∙109 cm-2. In general, H2 is not only a carrier gas, but also a reaction product in GaN growth and thus participates in the growth process. The role of H2 in the surface kinetics and its impact on layer quality and optical properties will thus be discussed. 

 

Legal notice
  • Legal notice:
 

Related papers

Presentation: Poster at 15th Summer School on Crystal Growth - ISSCG-15, by Evgenia Gridneva
See On-line Journal of 15th Summer School on Crystal Growth - ISSCG-15

Submitted: 2013-06-14 19:03
Revised:   2013-07-24 11:52