Hydrogen, microstructure and defect density in hydrogenated amorphous silicon

Abstract

It is well established that by bonding with the dangling bonds of silicon, hydrogen reduces the density of states of amorphous silicon and renders this material suitable to electronic applications. For so-called “standard” a-Si : H films deposited by the RF glow discharge decomposition of silane at low deposition rates (≈1 Å/s) and over a large range of deposition temperatures, we observed the usual correlation between the hydrogen bonding and the defect density in the as-deposited material only. It clearly appears that the widely accepted correlation between the hydrogen bonding, the microstructure and the defect density only applies to a limited set of deposition parameters. Moreover we found that the deposition of a-Si : H from mixtures of ...............

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

“…The analysis of the results indicates that annealing at 190 C, temperature very close to the equilibrium temperature value determined for good quality a-Si : H [36], produces a decrease in the native defects that have been formed during deposition. Similar results have been previously reported for PECVD films prepared in different conditions [7,29,37]. The fact that series II exhibits the lowest decrease in N D , suggests that this series has already optimised density of defects in the as-deposited state and it reaches thermal equilibrium during growth.…”

“…4. Example of optical absorption spectra obtained from PDS measurements for a) series III, b) IV and c) V in the as-deposited and annealed states as indicated have been reported for PECVD films prepared at lower substrate temperature (<200 C) [7,29,37,38]. The different slight decrease in N D observed for series I and III can be due to their different microstructure.…”

“…The total H content measured by ERDA is also shown in this table for comparison (Ref. [5]) the microstructure parameter R defined by the ratio of the integrated intensity of the 2080-2100 cm --1 stretching bands over the total integrated intensity of the stretching (2000 and 2080-2100 cm --1 ) band [7];…”

“…It is clearly established that deposition parameters such as substrate temperature, hydrogen and helium dilution and pressure play an important role on the quality of hydrogenated amorphous silicon (a-Si : H) and therefore on the light-induced metastability phenomena [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15]. This metastability, known as Staebler-Wronsky effect (SWE), is still not fully understood [16].…”

Polycrystalline Silicon Characteristics Dependence on Starting Amorphous Material

“…Such hypothesis is not surprising. Hence exodiffision of hydrogen from silicon occurs generally around 600°C and even at higher temperatures depending on the microstructure of the material [26]. Moreover infrared transmission measurements on T10-0, T30-0 and T100-0 show the presence of very weak absorption around 2000-2100 cm-' in T30-0 and T100-0 spectra.…”