Nanobeams for Nanoelectronice Devices - the Importance of ERL for Characterization of the Optoelectronic Device Structures
A.A. Sirenko1, A. Kazimirov2, D.H. Bilderback2, Z.-H. Cai3, and B. Lai3
1Department of Physics, New Jersey Institute of Technology
2Cornell High Energy Synchrotron Source, Cornell University
3Advanced
Photon Source, Argonne National Laboratory
Modern nanoelectronics is progressing from the planar epitaxial growth-based technology towards monolithic integration of multifunctional structures with complementary optical and electronic properties. Nanoscale selective area growth (NSAG) is a powerful technique for such integration, which holds a promise to improve both the optical properties and structural quality of the grown materials, and GaN-based device compounds in particular. The driving force behind these qualitative improvements is a more efficient bandgap engineering supported by strain relaxation at the sidewalls of the selectively grown nanostructures. A detailed analysis of the fundamental growth mechanisms and how they affect the structural and optical properties of the GaN-based NSAG structures is an important step towards their industrial applications.
The adequate characterization tools, such as synchrotron radiation based nanobeam high-resolution x-ray diffraction (HRXRD), are required to support the current trends in monolithic materials integration. Here we present our recent characterization results obtained with a nondestructive HRXRD technique and reciprocal-space-mapping (RSM) analysis with the spatial resolution on both micron and submicron scales. In particular, we have studied optoelectronic device structures produced in industrial fabrication facilities. Thickness, strain, composition variation, and details of the surface migration have been determined for various SAG ridge structures with active regions consisted of InGaAlAs/InP and InGaN/GaN multiple-quantum-wells (MQW) [1,2].
Our HRXRD experiments have been carried out at two synchrotron facilities: at A2 beamline at CHESS equipped with a one-bounce focusing capillary optics and at the APS 2ID-D microscope beamline equipped with a phase zone plate. The x-ray beamsize at CHESS was 10 mm and the beamsize at APS was 0.3 mm. High angular resolution for diffraction measurements was provided by a perfect crystal analyzer [e.g., Si(004) or Ge(111) ]. In our reciprocal-space-mapping (RSM) experiments at CHESS we have utilized a combination of the crystal-analyzer and a matching two-bounce channel cut crystal. The latter was positioned between the focusing capillary and the sample to condition the incident x-ray beam.
In this presentation we will also discuss the requirements for the future generation of the nanofocusing x-ray synchrotron facilities using three important parameters of the beamline setup: the flux as a number of photons seen by the detector (F), the beam-size on the sample (S), and the angular resolution (A). The figure of merit is the max for the following expression: F/(S×A). For example, at the 2-ID-D beamline we have F/(S×A) = 7´106 photons/(240 nm × 350nm × 2arcsec) » 50 photons/(nm2×arcsec). Efficient utilization of our experimental setup for RSM analysis of GaN-based nanostructures requires an increase of the photon flux by at least 1 order of magnitude and a decrease of the x-ray beamsize by another order of magnitude. It will allow us to combine RSM technique with real-space mapping of the next generation of nanoscale devices. This example highlights the importance of ERL for the development of the high resolution nanobeam diffraction techniques as adequate tools for characterization of the next generation of optoelectronic devices.
References:
[1] A. Kazimirov, A.A. Sirenko, D.H. Bilderback, Z-H. Cai, B. Lai, R. Huang, and A. Ougazzaden, J. Phys. D: Appl. Phys. 39, 1422–1426 (2006)
[2] A. Sirenko, A. Kazimirov, A. Ougazzaden, S. O’Malley, D.H. Bilderback, Z.-H. Cai, B. Lai, R. Huang, V. Gupta, M. Chien, S.N.G. Chu, Appl. Phys. Lett., 88, 081111 (2006)
