Evolution with light-soaking of polymorphous material prepared at 423 K

Light-induced defect creation in hydrogenated polymorphous silicon

“…However, the pm-Si:H film prepared at 150 • C exhibited a different behaviour from a-Si:H film prepared at 150 • C when the LS-annealing cycle was repeated, i.e., the improvement of the carrier diffusion length and the gradual reduction of the light-induced degradation efficiency when the sequences proceeded. These were attributed to the presence of platelets storing or releasing hydrogen into the network [12]. The results of annealing in air and in vacuum for our pm-Si:H powder samples prepared at 250 • C, particularly the result of the LS-annealing sequences, are similar to Roy et al's results on pm-Si:H film prepared at 150 • C, as will be shown below.…”

“…Our results also may be accounted for in terms of Roy et al's model that hydrogen is released and/or stored in the platelets and/or in voids as the forms of hydrogen molecules, hydrogen clusters or H * 2 complexes. It is noted that the sample of Roy et al was prepared at 150 • C, but the powder sample used in the present experiment was prepared at 250 • C. In Roy et al's experiment, samples prepared at 250 • C do not exhibit such LS-annealing cycles as observed in samples prepared at 150 • C. This is due to a different microstructure between two types of samples, as was pointed out by Roy et al [12]. Our powder samples were prepared in the atmosphere of mixture gas of SiH 4 and D 2 .…”

“…3(a and b) and 4 in the light of Roy et al's results [12]. As mentioned in Section 3, the light-induced degradation efficiency goes down with increasing annealing temperature except for the LS before annealing in air at 250 • C (Fig.…”

“…Before discussing the results of the LS-annealing sequences mentioned in Section 3, we cite recent results of Roy et al [12] on light-induced degradation of pm-Si:H films prepared at 250 and 150 • C. They measured the densities of states with the modulated photocurrent technique and the constant photocurrent method, the mobility-lifetime product of the majority carriers and the diffusion length of the minority carriers, repeating LS-annealing cycles, and compared the results of pm-Si:H films with those of a-Si:H films prepared at the same temperature. The pm-Si:H film prepared at 250 • C exhibited a similar behaviour to the a-Si:H film prepared at 250 • C when the LS-annealing cycle was repeated.…”

Device quality a-Si:H deposited from electron cyclotron resonance at very high deposition rates

“…It can be observed that L d , which is limited by the transport of holes in this type of material, increases when d increases, reaching a maximum value of 180 nm. These results compare favorably to those found for good quality a-Si:H samples and pm-Si:H samples [9]. The room temperature values of l n s n are found in the range 1.6 · 10 À7 and 2.7 · 10 À7 cm À2 V À1 for a dc generation rate (G dc ) around 2 · 10 19 cm À3 s À1 (Fig.…”