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HIGH-PRESSURE RAMAN SCATTERING OF BIAXIALLY STRAINED GaN ON GaAs
 

Summary: HIGH-PRESSURE RAMAN SCATTERING OF
BIAXIALLY STRAINED GaN ON GaAs
H. SIEGLE*, A. R. GONI*, C. THOMSEN*, C. ULRICH**, K. SYASSEN**,
B. SCHOTTKER***, D. J. AS***, D. SCHIKORA***
*Institut ftir Festk6rperphysik, TU Berlin, Hardenbergstrale 36, 10623 Berlin, Germany
**Max-Planck-Institut ffir Festk6rperforschung, Stuttgart, Germany
***Institut f'ir Optoelektronik, GHS Paderborn, Germany
ABSTRACT
We present results ofhigh-pressure Raman-scattering experiments on bulk GaN and GaN
grown on GaAs. We determined the Griineisen parameters of both the cubic TO and LO
phonon modes and the hexagonal A,, El and E2 modes. Our measurements reveal that the
Grtineisen parameters for the GaAs substrate are about 30% smaller than those of bulk GaAs.
This is a consequence of the lower compressibility of GaN compared to GaAs, which results
in a pressure-induced biaxial strain on the substrate. From the pressure behavior of the GaAs
modes and by comparing with our results for bulk GaN we obtained information about the
biaxial strain in the GaN epitaxial layer.
INTRODUCTION
A major problem in growing GaN layers on standard substrates as, e.g., sapphire, 6H-
SiC, or GaAs is the large lattice-mismatch and the difference in the thermal expansion
coefficients between layer and substrate. This causes a large biaxial stress in the layers, which

  

Source: As, Donat Josef - Department Physik, Universitšt Paderborn

 

Collections: Materials Science; Physics