| About this Abstract |
| Meeting |
2011 Electronic Materials Conference
|
| Symposium
|
2011 Electronic Materials Conference
|
| Presentation Title |
GG4, Microscopic Optical Properties of Semi-/Nonpolar GaN with InGaN SQWs on Top Grown Directly on Patterned Si Substrate |
| Author(s) |
Sebastian Metzner, Frank Bertram, Christopher Karbaum, Jürgen Christen, Shujian Liu, Natalia Izyumskaya, Vitaliy Avrutin, Ümit Özgür, Hadis Morkoç |
| On-Site Speaker (Planned) |
Sebastian Metzner |
| Abstract Scope |
Quantum structures for optoelectronic applications grown in the conventional c-direction are dramatically affected by the large spontaneous and piezoelectric polarization of the wurtzite crystal structure. Due to these built-in electric fields the electron and hole wave functions are locally separated inside the quantum well (QW) significantly reducing the overlap integral and hence the efficient radiative recombination in the QW known as quantum-confined Stark effect. One approach to overcome these impacts is the growth in semi- and nonpolar directions using patterned Si substrates and epitaxial lateral overgrowth as the usual semi/nonpolar heteroepitaxy leads to an insufficient crystal quality due to the lack of appropriate substrates apart from expensive and small bulk material. We have investigated semi- and nonpolar GaN templates and InGaN/GaN quantum structures which were grown by metal organic chemical vapor deposition directly on pre-patterned Si substrates using highly spatially and spectrally resolved cathodoluminescence (CL) at liquid He-temperature. The general idea is to initially grow (0001)GaN at {111} side facets of the grooved surfaces of Si substrates. For Si(112) substrates the trenches consist of vertical (-1-11) Si sidewalls and inclined (111) Si facets separated by terraces of residual Si(112). Except for the (-1-11) sidewall all other Si facets have been masked using SiO<sub>2</sub>, hence, the final GaN crystal orientation forms a planar m-plane surface. Additionally, a saw tooth-like semipolar (10-11) GaN surface was grown on the patterned Si(112) substrate. For Si(001) substrates the (1-1-1) Si sidewall is inclined and single GaN stripes with semipolar (1-101) facets form the surface. All sample structures were finally used as a template for an InGaN/GaN SQW. Using Si(112), the +c-wing of the GaN structure with a semipolar surface shows a homogeneous and slightly red-shifted (D<sup>0</sup>,X) emission at 3.463 eV (358 nm) with a FWHM of about 8 meV. In local spectra from the –c-wing two strong luminescence contributions from basal plane stacking faults (BSF) at 3.418 eV and 3.410 eV can be observed which can be directly attributed to the emission from short and elongated BSFs, respectively. The CL intensities of (D<sup>0</sup>,X) and BSF are locally perfectly anticorrelated. The partially coalesced m-plane GaN structure with an InGaN SQW atop exhibits an intense quantum well luminescence which is centered at about 3.2 eV, having a FWHM of 98 meV. Strong and homogeneous CL from the SQW is emitted from nearly the entire m-plane surface. Just above the –c-wing the InGaN luminescence is reduced due to the presence of stacking faults and defects. In absolute contrast no BSF luminescence is found at the +c-wing where (D<sup>0</sup>,X) GaN and the InGaN QW dominate. |
| Proceedings Inclusion? |
Undecided |