Effect Of Sulfur Passivation Research Articles

Surface Passivation of Crystalline Silicon Wafer Using H2S Gas

We report the effects of H2S passivation on the effective minority carrier lifetime of crystalline silicon (c-Si) wafers. c-Si wafers were thermally annealed under an H2S atmosphere at various temperatures. The initial minority carrier lifetime (6.97 μs) of a c-Si wafer without any passivation treatments was also measured for comparison. The highest minority carrier lifetime gain of 2030% was observed at an annealing temperature of 600 °C. The X-ray photoelectron spectroscopy analysis revealed that S atoms were bonded to Si atoms after H2S annealing treatment. This indicates that the increase in minority carrier lifetime originating from the effect of sulfur passivation on the silicon wafer surface involves dangling bonds.

Effects of Sulfur Passivation on 6H-SiC(0001) Surface and Si/6H-SiC Interface

The un-passivated and passivated 6H-SiC(0001) surface and Si(-220)/6H–SiC (0001) interface are investigated by first-principles calculation based on density functional theory. It is demonstrated that the surface energy of 6H-SiC(0001) surface with seven atom-layers converges well. When the surface is passivated with sulfur(S), the density of states decreases obviously, implying that the passivated 6H-SiC(0001) surface are more stable. Four specific geometry models of Si(-220)/6H–SiC(0001) interface structures with different terminations are chosen. The calculated adhesion energies suggest that, for un-passivated interface, the atomic binding force and interface stability of C-termination interface are stronger than Si-termination interface, while for passivated interface, the tendency is opposite. The calculations about the density of states of un-passivated interfacial suggest that the Si-Si covalent bonds are formed at Si-terminated interface, and that C-Si covalent bonds are formed at C-terminated interface. After the interface is passivated with S atoms, the interaction between Si and S atoms is observed.

Sidewall passivation for InGaN/GaN nanopillar light emitting diodes

We studied the effect of sidewall passivation on InGaN/GaN multiquantum well-based nanopillar light emitting diode (LED) performance. In this research, the effects of varying etch rate, KOH treatment, and sulfur passivation were studied for reducing nanopillar sidewall damage and improving device efficiency. Nanopillars prepared under optimal etching conditions showed higher photoluminescence intensity compared with starting planar epilayers. Furthermore, nanopillar LEDs with and without sulfur passivation were compared through electrical and optical characterization. Suppressed leakage current under reverse bias and four times higher electroluminescence (EL) intensity were observed for passivated nanopillar LEDs compared with unpassivated nanopillar LEDs. The suppressed leakage current and EL intensity enhancement reflect the reduction of non-radiative recombination at the nanopillar sidewalls. In addition, the effect of sulfur passivation was found to be very stable, and further insight into its mechanism was gained through transmission electron microscopy.

Sulfur passivation and contact methods for GaAs nanowire solar cells

The effect of sulfur passivation on core–shell p–n junction GaAs nanowire (NW) solar cellshas been investigated. Devices of two types were investigated, consisting of indium tinoxide contact dots or opaque Au finger electrodes. Lateral carrier transport from the NWsto the contact fingers was achieved via a p-doped GaAs surface conduction layer. NWsbetween the opaque contact fingers had sidewall surfaces exposed for passivation by sulfur.The relative cell efficiency increased by 19% upon passivation. The contribution of thethin film grown between the NWs to the total cell efficiency was estimated byremoving the NWs using a sonication procedure. Mechanisms of carrier transport andphotovoltaic effects are discussed on the basis of spatially resolved laser scanningmeasurements.

Effect of sulfur passivation on the InP surface prior to plasma-enhanced chemical vapor deposition of SiNx

The fabrication of Au/SiNx/InP metal–insulator–semiconductor (MIS) diodes has been achieved by depositing a layer of SiNx on the (NH4)2Sx-treated n-InP. The SiNx layer was deposited at 200 °C using plasma-enhanced chemical vapor deposition (PECVD). The effect of passivation on the InP surface before and after annealing was evaluated by current–voltage (I–V) and capacitance–voltage (C–V) measurements, and Auger electron spectroscopy (AES) analysis was used to investigate the depth profiles of several atoms. The results indicate that the SiNx passivation layer exhibits good insulative characteristics. The annealing process causes distinct inter-diffusion in the SiNx/InP interface and contributes to the decrease of the fixed charge density and minimum interface state density, which are 1.96 × 1012 cm−2 and 7.41 × 1011 cm−2 eV−1, respectively. A 256 × 1 InP/InGaAs/InP heterojunction photodiode, fabricated with sulfidation and SiNx passivation layer, has good response uniformity.

Effects of Sulfur Passivation on Germanium MOS Capacitors With HfON Gate Dielectric

In this letter, we study the effects of sulfur (S) passivation, using aqueous ammonium sulfide ((NH <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</sub> ) <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> S), on germanium (Ge) MOS capacitors with sputtered HfON as gate dielectric and TaN as metal-gate electrode. Compared with control samples, the S passivation can effectively reduce both equivalent oxide thickness and interface-state density. X-ray-photoelectron-spectroscopy analysis shows that (NH <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</sub> ) <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> S treatment can reduce the Ge-O bonds on Ge surface. The thermal stability of the S passivation under different postmetal-annealing temperatures was also examined, and it was found that samples with (NH <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</sub> ) <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> S treatment exhibit stable Ge/high-fc interface upon 550-deg C postmetal-deposition annealing, whereas interface quality degrades for those samples without S passivation.

Effect of sulfur passivation and polyimide capping on InGaAs-InP PIN photodetectors

It is shown in this work that sulfur passivation followed by a deionized water rinse reduces the dark current of InGaAs-InP PIN photodetectors significantly. This reduction in dark current is shown to be due to reduced recombination at the exposed mesa surface. Detectors with polyimide capping after sulfur passivation showed no degradation in characteristics with time.

The Effect of Sulfur Passivation and Rapid Thermal Annealing on the Properties of InAs MOS Structures with the Oxide Layer Deposited by Reactive Sputtering

The effect of rapid thermal annealing and sulfur passivation on the quality of reactively sputtered SiO2 on InAs were investigated. Results show that both rapid thermal processing and sulfur passivation cause a reduction in leakage current and oxide fixed charges. Annealing at temperature higher than 400 °C caused degradation. Also passivation started to loose its effectiveness when structures are annealed at 500 °C.

Reduction of gap states of ternary III–V semiconductor surfaces by sulfur passivation: Comparative studies of AlGaAs and InGaP

The effects of sulfur passivation on liquid-phase-epitaxy-grown n-type InGaP and AlGaAs surfaces have been studied using x-ray photoelectron spectroscopy. The surfaces were simultaneously prepared through degreasing and the use of an aqueous (NH4)2Sx treatment in air. For InGaP, sulfur atoms initially reacted with both surface In and Ga atoms and reacted negligibly with P atoms. The band bending was reduced by 0.7 eV compared to a sputter-cleaned surface. Presumably, sulfur eliminated P-vacancy-related gap states by occupying P sites and forming In–S and Ga–S bonds. By postheat treatment at 180 °C, S atoms were not removed from the surface and band bending was reduced further by 0.1 eV. For AlGaAs, S atoms initially reacted with Ga and As, but this treatment could not remove the Al oxide previously formed in the air. Postheat treatment at 180 °C simply induced S redistribution from As to Ga and As desorption, which reduced the band bending by 0.3 eV compared to the sputter-cleaned surface—a result similar to that for GaAs.

Effects of sulfur passivation and rapid thermal annealing on the electrical properties of InP metal–insulator semiconductor Schottky diodes

The effects of sulfur passivation and rapid thermal annealing on the electrical characteristics of InP metal–insulator semiconductor Schottky diodes are investigated. Passivation causes a moderate increase in barrier height and decrease in reverse current. Further reduction in the reverse current is obtained after rapid thermal annealing. The passivated diodes show a very good thermal stability. Bond formation at the interface and charge injection into the oxide are used to explain the observations.