D. Mao et Pc. Taylor, OPTICALLY DETECTED ESR STUDIES OF RECOMBINATION PROCESSES IN A-SI-H, Journal of non-crystalline solids, 190(1-2), 1995, pp. 48-57
A study of recombination processes in high-quality (intrinsic) and lig
ht-soaked hydrogenated amorphous silicon (a-Si:H) using the technique
of optically detected electron spin resonance (ODESR) is reported. A t
ime-domain detection scheme is employed, instead of the conventional l
ock-in technique, to record the ODESR lineshapes, which effectively mi
nimizes the well-known interference between the 'enhancing' and 'quenc
hing' signals. Monitoring the photoluminescence (PL), below 1.1 eV, in
the intrinsic sample, a nearly symmetric enhancing signal (g = 2.008)
related to radiative recombination of spin pairs in shallow band-tail
states and an asymmetric quenching signal (g = 2.005) related to non-
radiative recombination of spin pairs in deep band tail states are obs
erved. A quenching signal at half-field (g similar or equal to 4) is a
lso observed. The light-soaked sample exhibits an additional signal (g
= 2.006) which is related to the dangling bonds. The PL excitation en
ergy, E(x), is varied from above to below the optical gap to study pos
sible changes in the recombination processes. It is found that the ODE
SR lineshapes are essentially the same for E(x) > 1.5 eV and some subt
le changes occur for E(x) <1.5 eV. The signal intensity, however, depe
nds strongly on the excitation energy for a constant electron-hole pai
r generation rate.