Efficient passivation of n-type and p-type silicon surface defects by hydrogen sulfide gas reaction

Abstract

An efficient surface defect passivation is observed by reacting clean Si in a dilute hydrogen sulfide-argon gas mixture (<5% H 2 S in Ar) for both n-type and p-type Si wafers with planar and textured surfaces. Surface recombination velocities of 1.5 and 8 cm s −1 are achieved on n-type and p-type Si wafers, respectively, at an optimum reaction temperature of 550 • C that are comparable to the best surface passivation quality used in high efficiency Si solar cells. Surface chemical analysis using x-ray photoelectron spectroscopy shows that sulfur is primarily bonded in a sulfide environment, and synchrotron-based soft x-ray emission spectroscopy of the adsorbed sulfur atoms suggests the formation of S-Si bonds. The sulfur surface passivation layer is unstable in air, attributed to surface oxide formation and a simultaneous decrease of sulfide bonds. However, the passivation can be stabilized by a low-temperature (300 • C) deposited amorphous silicon nitride (a-Si:N X :H) capping layer.

Atomic and molecular functionalisation of technological materials: an introduction to nanoscale processes on semiconductor surfaces

“…Chemical understanding of passivating silicon surface defects by hydrogen sulfide is relevant directly to the application of this material in solar cells. The paper by Das et al [4] addresses the chemistry of the passivation process and connects fundamental properties with the measurements that are needed to asses the device performance.…”