USE OF THE STEADY-STATE PHOTOCARRIER-GRATING TECHNIQUE FOR THE STUDY OF THE SURFACE RECOMBINATION VELOCITY OF PHOTOCARRIERS AND THE HOMOGENEITY OF HYDROGENATED AMORPHOUS-SILICON FILMS

The principle of using the steady-state photocarrier grating (SSPG) technique to determine the surface recombination velocity s of excess carriers is described. It is shown that, by using excitation light of sufficiently high absorption constant, one can measure both s and the ambipolar diffusion length of photocarriers. Ar laser illumination was used to measure s at both the air-film and the film-substrate interfaces of a typical undoped hydrogenated amorphous Si (a-Si:H) sample. Surface recombination velocities of 720 and 2770 cm s-1 were obtained for the air-side and substrate-side illuminations respectively. These results are consistent with those obtained from the spectral dependence of the photoconductivity of the same sample. It is also shown that using the SSPG technique the homogeneity in the growth direction of a-Si:H films can be investigated.