Residual strain field in indented GaAs
- PDF / 285,763 Bytes
- 7 Pages / 612 x 792 pts (letter) Page_size
- 48 Downloads / 161 Views
Paulo Sergio Pizani Departamento de Fisica, Universidade Federal de São Carlos, C.P. 369, 13560-970 São Carlos, SP, Brazil
Samuel Wey LPST—UMR 5477 CNRS, Université Paul Sabatier, 118 route de Narbonne, 31062 TOULOUSE Cedex, France
Chantal Fontaine LAAS—UPR 8001 CNRS, avenue du Colonel Roche, 31077 TOULOUSE, Cedex, France (Received 20 November 2002; accepted 27 March 2003)
This paper presents an optical mean to probe carefully the strain field generated by a microindentation on [111]-oriented GaAs sample, using micro-Raman spectroscopy and microphotoluminescence spectroscopy. Raman and photoluminescence signals recorded from the same point of the sample are directly compared. The frequency shift of the longitudinal and transverse optical phonons was analyzed in great detail, revealing unambiguously the presence of both compressive and tensile strains within the indented area. Outside the indentation fingerprint, the magnitude of strain deduced from luminescence measurements was found to be lower than the one determined by Raman scattering. The Raman spectra revealed significant variations of the optical phonons polarizability with the deformation. Finally, atomic force microscope images of the indented zone aid in the interpretation.
I. INTRODUCTION
Microindentation, nanoindentation, and micromachining are currently used in materials science mainly to test and study the mechanical properties at the microscopic scales. In the last decade, elemental semiconductors such as germanium and silicon have drawn much attention, in particular for the study of their properties under pressure.1,2 For silicon, it is now well known that the material undergoes a phase transformation toward the Si-II Sn metallic phase, transforming into various Si polymorphs upon depressurization,3 which were discovered by Raman spectroscopic signatures. Mechanical properties of III-V polar semiconductors like GaAs have not been investigated as much.4–7 This is partly explained by the extreme fragility of this material and almost precludes any machining.8 We have found that the collected Raman scattering signal in GaAs is 15 times lower than in Si, which renders spectroscopic analysis more difficult.9 In the present work, we focused our attention to the strain field in indented GaAs and compared Raman and photoluminescence (PL) measurements. The sample was grown by molecular beam epitaxy (MBE) along [111] orientation. This crystallographic orientation provides 1474
http://journals.cambridge.org
J. Mater. Res., Vol. 18, No. 6, Jun 2003 Downloaded: 25 Apr 2015
the possibility to observe by Raman selection rules both transverse optical (TO) and longitudinal optical (LO) phonons as compared to the [001] orientation, which allows observation of only the LO mode.10,11 We will discuss the negative shift of the LO mode in previous work, which was suspected to originate from spatial correlation. Great attention was paid to the experimental precautions. The aim of this paper is to report a careful study of the residual strain in microindented GaAs, to
Data Loading...
