INTEC   05402
INSTITUTO DE DESARROLLO TECNOLOGICO PARA LA INDUSTRIA QUIMICA
Unidad Ejecutora - UE
congresos y reuniones científicas
Título:
CHARACTERIZATION OF HYDROGENATED AMORPHOUS SILICON BY MEANS OF PHOTOGENERATED OPTICAL GRATINGS
Autor/es:
F. VENTOSINOS; F. MORA OCHOA; J. A. SCHMIDT
Lugar:
Cancun
Reunión:
Congreso; XXI International Materials Research Congress; 2012
Institución organizadora:
Sociedad Mexicana de Materiales and The Materials Research Society
Resumen:
Amorphous semiconductors with electronic applications are extensively studied because of the possibility of making thin-film devices. Being hydrogenated amorphous silicon (a-Si:H) one of the most widely used materials in thin-film electronics, the study of characterization techniques that could give in a simple and fast way information on its properties is a trend topic for the scientific community. One of these techniques was proposed in 1993 by Hattori et al.1 The Modulated Photocarrier Grating (MPG) technique consist in making two coherent laser beams interfere over a sample with coplanar geometry. Using an electro optic modulator (EOM) to rotate the polarization of one of these beams at a frequency ω, leaving the other one with a fixed linear polarization, gives an interference pattern whose contrast varies with time. Hattori et al.1 used the above experimental configuration to achieve a generation rate modulated both in space and time. By measuring the resulting photocurrent they estimated the diffusion length of minority carriers. Later, Schmidt et al.2 showed that, under certain conditions, using MPG together with a related technique (modulated photoconductivity, MPC3) could give information on the density of states (DOS) in the subgap region. However, to rotate the polarization of a beam at high frequencies is a difficult task. In this work we present a different experimental configuration to achieve the same generation rate without having troubles at high frequencies. We use an EOM to switch the polarization of the laser beam between linear and slightly elliptical, a cube beamsplitter to separate both polarization components and a half wavelength plate to rotate by 90º the polarization of one of the beams, so that they interfere. This configuration gives us the opportunity to measure both MPG and MPC techniques just by blocking the less-intense beam. We present experimental and simulated result to test this promising new configuration.