Al-H and Al-D complexes in Si: A uniaxial-stress study of the hydrogen vibrational modes

Abstract

Perturbation of the 2201-cm Ϫ1 absorption line of the Al-H complex in Si by uniaxial stress is shown to be consistent with a stretching mode of a center with an effectively trigonal symmetry. Quantitative analyses of the effects of the stresses and of varying the temperature reveal the presence of a very-low-frequency transverse mode which transforms as the E irreducible representation in the trigonal symmetry. Its frequency is 64 cm Ϫ1 in the ground state of the stretching mode ͑representation A 1 ͒. An A 1 ϩE combination mode, observed only under stress, lies 24 cm Ϫ1 above the excited state of the A 1 mode. Upon substituting D for H, the frequencies of the stretching and transverse modes are reduced by approximately a factor of 1/&, as expected for vibrations which predominantly involve the H ͑D͒ atom. The symmetries of the center and of its modes are unchanged by the isotopic substitution. The Al-H axis may be preferentially aligned along one of the ͗111͘ axes by an applied stress. The barrier to reorientation is ϳ370 meV. ͓S0163-1829͑96͒03139-6͔

Hydrogen motion in the Cu-H complex in ZnO

“…Two defects, B-H and Al-H, were investigated and it was found that E a Ϸ 0.2 eV for the B-H complex, 26 whereas E a = 0.37 eV for hydrogen bound to Al. 27 Obviously, of these two complexes, it is Al-H that has to be compared with isolated hydrogen since Al and Si are next neighbors in the Periodic Table. Indeed, in this case, the activation barrier for hydrogen reorientation in the Al-H complex is only 20% off from E a of isolated hydrogen.…”

“…Such frequencies are typical for hydrogen-related defects in other semiconductors and characterize hydrogen vibrations. [24][25][26][27][28][29] The reorientation temperature, on the other hand, is very sensitive to the value of E a . From the data shown in the figure, we find that E a = 0.52± 0.04 eV.…”

Uniaxial stress study of the Cu–H complex in ZnO

“…At elevated temperatures a side-band shifted downwards in energy from the main line appears in the spectra [14]. Uniaxial stress also results in a side-band due to the coupling of the main mode with the thermally populated excited state [15]. The activation energies of the side-bands are in the range of 60-180 cm 1 -and seem to depend on the hydrogen isotope approximately as 1 m / [14,16].…”

Hydrogen motion in rutile TiO2

“…The advantage of stress-induced dichroism stems from the fact that it allows to probe an elementary diffusion step—a jump between the two neighboring lattice sites. Indeed similar experiments performed for hydrogen-related defects in Si 22 _ 24 , GaAs 25 , 26 , ZnO 27 , 28 , and very recently In 2 O 3 29 provided a great deal of insight in the kinetics of hydrogen motion in these semiconductors.…”