Passivation study of the amorphous–crystalline silicon interface formed using DC saddle‐field glow discharge

Abstract

Phone: þ00 1 416 946 7372, Fax: þ00 1 416 971 2326The DC saddle-field (DCSF) glow discharge method was used to deposit intrinsic a-Si:H onto c-Si to passivate the c-Si surface. The effective minority carrier lifetime in the heterostructures as a function of the excess minority carrier density in the c-Si wafers was measured. The results were then analyzed in the context of recombination associated with interface defect states using three known recombination models. The defect density and the charge density at the interface are inferred. In addition subsequent annealing of the samples was studied. It is shown that for our intrinsic a-Si:H samples improvements in surface passivation are directly correlated with the reduction of interface defects and not the reduction of minority carrier concentration at the interface due to electric field. We have achieved excellent surface passivation with effective carrier lifetime >4 ms for an intrinsic a-Si:H sample deposited at a process temperature of 200 8C and thickness of about 30 nm. It is also demonstrated that subsequent annealing, at 240 8C, of the samples which were prepared at process temperatures <240 8C greatly increases the effective lifetime.

High quality amorphous–crystalline silicon heterostructure prepared by grid-biased remote radio-frequency plasma enhanced chemical vapor deposition

“…2, N s changes significantly with samples prepared using different conditions, however, the fitted Q s for all samples remained constant at approximately 1.0×10 11 cm −2 . This is consistent with results reported in other studies [6,14] which show that N s is the primary parameter which determines the passivation quality for samples passivated with intrinsic a-Si:H (e.g., i-a-Si:H/n-c-Si/ i-a-Si:H). As a result, only the N s values for different samples are quoted in the remaining sections of this paper.…”

“…In this paper, the interface defect density is inferred by applying a simple closed form (SCF) model described in detail in [14,32]. This model has two variable parameters -the interface defect density (N s ) and the interface charge density (Q s ).…”

“…Alternative techniques, such as electron cyclotron resonance based on microwave assisted magnetically confined plasma [13], DC saddlefield PECVD [14], and hot-wire CVD [15,16], have also been explored, showing remote plasma and plasma-free deposition capabilities. Nevertheless, RF [12] and VHF PECVD [17,18] currently appear to be the mainstay in the industry for amorphous-crystalline silicon heterojunction synthesis given that these techniques are well-established production platforms.…”

Interface properties of amorphous-crystalline silicon heterojunctions prepared using DC saddle-field PECVD

“…In the present study, the cathodes and the substrate were all held at ground potential. Using this DC saddle field configuration in a previous study we have reported passivation results showing effective lifetimes exceeding 1 ms [3].…”

“…This saddle-field configuration promotes the oscillation of electrons about the anode, resulting in a much longer electron mean free path, which in turn increases the probability of interaction with gas-phase species and thus allows for a stable plasma at much lower pressures than is normally possible with a DC diode. The semi-transparent cathode, which permits plasma species to diffuse to the substrate, serves to isolate the substrate from the plasma region proper thereby allowing the plasma parameters and the substrate parameters to be controlled independently [3,4]. In addition to the remote plasma, the energy of the ionic species arriving at the substrate can be modulated by varying the substrate and semitransparent cathode potentials.…”