Structural characterization of superlattice of microcrystalline silicon carbide layers for photovoltaic application

Abstract

We have systematically studied a series of silicon carbide multilayer (#SiC) samples, each consisting of 30 periods of two alternating layers of microcrystalline silicon carbide (lc-SiC:H) having identical band gap of 2.2 eV but different amount of crystalline silicon volume fraction. The thickness of the lc-SiC:H layer deposited at higher power (termed as HPL) with higher degree of crystallinity was kept fixed at a value of 5 nm, while the thickness of the other lc-SiC:H layer deposited at a lower power (termed as LPL) was changed from 13 nm to 2 nm for the different samples of the series. With lowering of the LPL thickness, a decrease in the void fraction together with an improvement in the short range order within the multilayered samples was observed. By decreasing the thickness of the LPL layer up to 2 nm, the photoluminescence study indicates the formation of an intermediate band within the superlattice of lc-SiC:H. Photovoltaic properties of this superlattice layer were investigated in a p-i-n diode structure. V C 2013 American Institute of Physics. [http://dx.

Growth of silicon quantum dots by oxidation of the silicon nanocrystals embedded within silicon carbide matrix

“…The 2.1 eV peak has been observed in our earlier stuy on µc-SiC:H superlattice samples. 6 We explained this peak on the basis of a radiative tunneling between the band tail states as occurs in a-Si:H. 33 The origin of the 2.1 eV PL peak may also arise in this case from a defect state in SiO 2 . 34 The lower energy peak at 1.8 eV may be due to the nc-Si grains showing confinement effect.…”

“…[2][3][4] Regular arrangement of Si-QDs may be achieved by the formation of superlattices of the Si-QD layers sandwiched between layers of dielectric. Si-QD solar cells have been described by forming superlattice of Si-QDs with amorphous silicon 5 or amorphous silicon carbide 6 used as the absorbing layers with controllable band gap. However, due to low band gap of 2.5 eV for SiC in comparison with Si 3 N 4 (∼5.3 eV) or SiO 2 (∼9 eV), the Si-QD / SiC barrier height is also low.…”

Electrical transport in transverse direction through silicon carbon alloy multilayers containing regular size silicon quantum dots

“…The deposition time for the LPL/HPL layer in each cycle were controlled in order to get the desired thickness (Table 2) as per the known growth rates ( Table 1). The individual thicknesses of the HPL and LPL layers were acquired from ellipsometric measurements [21] and indicated in Table 2. For one sample (#SiC-ML4), the overall thickness has been verified by the cross sectional TEM measurement as will be discussed later in Section 3.…”

“…In this respect, low temperature growth of high quality amorphous or microcrystalline group IV materials (Si, Ge, C) and their alloys by PECVD method has prompted many researchers to study superlattice/multilayers of these materials [20]. In our previous studies, we have demonstrated the photovoltaic effects of Si-QD embedded hydrogenated silicon carbon alloy (SiC:H) multilayers consisting of the alternating layers of a nearly amorphous silicon carbide (a-SiC:H) and a microcrystalline silicon carbide (c-SiC:H) containing high density of Si-QDs grown at low deposition temperatures (~ 200C) in a PECVD system [21]. We also studied the structural properties such as crystalline volume fraction of Si, voids, PL response in a series of such multilayers [21,22].…”

“…In our previous studies, we have demonstrated the photovoltaic effects of Si-QD embedded hydrogenated silicon carbon alloy (SiC:H) multilayers consisting of the alternating layers of a nearly amorphous silicon carbide (a-SiC:H) and a microcrystalline silicon carbide (c-SiC:H) containing high density of Si-QDs grown at low deposition temperatures (~ 200C) in a PECVD system [21]. We also studied the structural properties such as crystalline volume fraction of Si, voids, PL response in a series of such multilayers [21,22]. It is also important to understand the correlation between the microstructures present within the materials and the corresponding electrical transport mechanism for their optoelectronic applications.…”