The Role of Hydrogen in the Staebler-Wronski Effect of a-Si:H

Abstract

We have studied the effects of hydrogen concentration and hydrogen configuration on the light-induced change, called Staebler-Wronski effect, in a-Si:H. A strong correlation is found between the light-induced spin density and the fractional hydrogen content evolved at low annealing temperature. The light-induced defects are supposed to be created through the breaking of weak Si-Si bonds in the regions containing clustered SiH or SiH2 bonds.

Anneal treatment to reduce the creation rate of light-induced metastable defects in device-quality hydrogenated amorphous silicon

“…The reduced LI-DB creation occurs above an "onset temperature" of about 350°C with no measurable reduction at lower anneal temperatures. Similar onset temperatures have been observed in thicker films by several hours exposure to solar spectrum light, 3,4 however these workers never demonstrated lower total defect densities in the light exposed, annealed films. The 350°C anneal reduces LI-DB creation by almost a factor 2 with only about a factor of 2 increase in the native DB concentration.…”

“…An alternative postdeposition treatment, thermal annealing at elevated temperatures, [3][4][5] has reduced light-induced degradation in preliminary experiments but careful follow-up experiments on these findings have not been extensive.…”

Effect of the Nature of the Hydrogen Bonding on the Light-Induced Metastable Defects in Hydrogenated Amorphous Silicon Prepared by Radiofrequency Magnetron Sputtering

“…The most photodegraded films are, in fact, those of series V, due to the presence in these films of high amount of structural inhomogeneities, such as microvoids, as it has been previously reported [13,39,44]. Moreover, we demonstrate that the light-induced effects strongly depend on the nature of the hydrogen bonding configurations and their relative proportion, which are directly linked to the structural inhomogeneities, rather than on the total bonded hydrogen content itself [5,33,34,45,46]. We observe, indeed, that the photodegradation of the films increases, as E 0 , measured in the deposited state, is larger.…”

Structural properties of hot wire a-Si:H films deposited at rates in excess of 100 Å/s

“…Carlson first presented a model involving the motion of H on the internal surfaces of microvoid surfaces, 40,41 based on the assumption that holes can be trapped on weak Si-Si bonds existing near these surfaces. Osawa et al 45 provided experimental evidence for this model by correlating an increased light-induced electron spin resonance spin density with the fractional H content evolved at low anneal temperatures; this evolving H was suggested to be clustered H bonded in some fashion ͑mono-, dihydride͒ on ͑interconnected͒ microvoid surfaces. Bhattacharya and Mahan 23 then showed, using R*, that samples with more microstructure showed an increased light induced effect.…”