Abstract
A depth-resolved study of the optical and structural properties of wurtzite InGaN/GaN bilayers grown by
metallorganic chemical vapor deposition on sapphire substrates is reported. Depth-resolved cathodoluminescence
(CL) and Rutherford backscattering spectrometry (RBS) were used to gain an insight into the compositional
profile of a 75-nm thick InGaN epilayer in the direction of growth. CL acquired at increasing electron
energies reveals a peak shift of about 25 meV to the blue when the electron beam energy is increased from 0.5
to ~7 keV, and shows a small shift to lower energies between ~7 and 9 keV. For higher accelerating voltages
the emission energy peak remains constant. This behavior can be well accounted for by a linear variation of In
content over depth. Such an interpretation conforms to the In/Ga profile derived from RBS, where a linear
decrease of the In mole fraction from the near surface (~0.20) down to the near GaN/InGaN interface (~0.14)
region fits the random spectra very well. Furthermore, by measuring the tetragonal distortion at different
depths, using RBS/channeling, it is shown that regions of higher In content also appear to be more relaxed.
This result suggests that strain hinders the incorporation of In atoms in the InGaN lattice, and is the driving
force for the compositional pulling effect in InGaN films.
Original language | English |
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Pages (from-to) | 205311-1 |
Number of pages | 205310 |
Journal | Physical Review B: Condensed Matter and Materials Physics |
Volume | 64 |
Issue number | 205311 |
DOIs | |
Publication status | Published - 2 Nov 2001 |
Keywords
- pulling effects
- InxGa1-x N/GaN layers
- cathodoluminescence
- Rutherford backscattering
- channeling
- nanoscience