Optimum doping level in a-Si:H and a-SiC:H materials

Abstract

The changes in the optical and electrical properties of thick a-Si:H and a-SiC:H films doped with diborane are investigated. In situ spectroscopic ellipsometry measurements reveal that, at a ratio of diborane to silane Cg=[B2H6]/[SiH4]<10−3, the optical properties of both materials are not strongly modified by boron doping. However, in the case of a-Si:H films, an improvement of the morphological and optical properties is observed at Cg=0.45×10−3. The existence of an optimum doping level at Cg<10−3 in the case of an a-Si:H p layer is confirmed by the dependence of the open-circuit voltage of a-Si:H based solar cells on the doping level of the p layer.

Structure and optical properties of aSiAl and aSiAlHx magnetron sputtered thin films

“…They attributed that to the increased material density and to the decreased hydrogen concentration of the film. 16 The results from Hadjadj et al 16 are in agreement with our results, showing that an increased hydrogen content in the film lowers the refractive index. This is probably due to both the passivation of dangling bonds and a decrease in the film density.…”

“…They attributed the reduced refractive index to the increased internal strain. However, Hadjadj et al 16 found that the refractive index increased strongly for boron doping concentrations above 10 [B 2 H 6 ]/[SiH 4 ]. They attributed that to the increased material density and to the decreased hydrogen concentration of the film.…”

Complex study of mechanical properties of a-Si:H and a-SiC:H boron doped films

“…The slope of the valence band tail E OV (see Table 1), which is an indicator of disorder in the material, is higher for the doped a-SiC:H films than for the doped a-Si:H. In our previous paper [1] the poorer morphology of the aSiC:H alloys compared to the a-Si:H and the smaller effect of the boron doping on their properties was discussed. These results are in very good agreement with the microhardness measurements.…”

“…Boron doped a-Si:H and a-SiC:H, 0.54-0.68 lm thick films were deposited on Corning glass substrates at 180°C by RF glow discharge decomposition of 10 sccm of silane mixed with either diboran or trimethylboron diluted at 2% in hydrogen [1,2]. The boron doped silicon-carbon alloys (a-SiC:H) usually used as window layers in solar cells were produced by the decomposition of the mixture of 50% silane and methane.…”

Effect of Oxygen and Diborane Gas Ratio on P-type Amorphous Silicon Oxide films and Its Application to Amorphous Silicon Solar Cells

“…The Si-O-Si bridge has a stronger bond energy compared to the Si-Si bond energy due to either a decrease in the band width or an increase in the energy difference between bonding and anti-bonding splitting regarding Si-Si derived bonds [12]. The bond energies for the Si-O bond in SiO 2 and the Si-Si bond in c-Si appears to be 4.8 eV and 2.3 eV, respectively [13]. The B 2 H 6 often attributed to the increase of disorder in the network and the removal of oxygen from the p-type a-SiO x :H films.…”