Effects of damages induced by indium-tin-oxide reactive plasma deposition on minority carrier lifetime in silicon crystal

Takefumi Kamioka,Atsushi Ogura,Yutaka Hayashi,Yoshio Ohshita,Yuki Isogai

doi:10.1063/1.5124903

Takefumi Kamioka, Atsushi Ogura + Show 3 more

Open Access

https://doi.org/10.1063/1.5124903

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Journal: AIP Advances	Publication Date: Oct 1, 2019
Citations: 8	License type: cc-by

Affiliation: Meiji University, Toyota Technological Institute

Abstract

A reactive-plasma deposition (RPD) process damage is evaluated for an indium-tin-oxide (ITO)/SiO2/Si structure in terms of the recombination properties at the interface. To calculate the surface recombination velocity (SRV), the defect density at the SiO2/Si interface (Dit), the effective total charge (Qtot) which is the sum of the charges in the SiO2 and the trapped charge at the SiO2/Si interface, and the workfunction of ITO at the ITO/SiO2 interface (ϕITO), are extracted by capacitance-voltage (C-V) analysis as a function of a postdeposition annealing (PDA) temperature. The Dit and Qtot significantly increase by the RPD process to 1.4×1012 cm-2eV-1 and 1.5×1012/q cm-2, respectively, and decrease by the PDA at 200 °C in N2 ambient to 1.4×1011 cm-2eV-1 and 1.1×1011/q cm-2, respectively. The ϕITO also varies from 4.80 eV to 4.35 eV by the PDA. The correlation is examined between the SRV values calculated based on the extended SRH model using the extracted Dit, Qtot, and ϕITO values [SRV(CV)], and the SRV ones obtained from the minority carrier lifetime measurements [SRV(LT)]. It is found that multiple sets of capture cross-sections were required for SRV(CV) values to coincide with SRV(LT) ones. The effect of variation in the Qtot and ϕITO on the band bending is almost canceled out in the present PDA condition. It is thus considered that the increase in Dit is the main cause to decrease the minority carrier lifetime.

Highlights

Indium-tin oxide (ITO) is a material widely used for optoelectronic device applications such as solar cells,[1,2] charge-coupled devices (CCDs)[3,4,5] and light emitting diodes (LEDs).[6,7] ITO films for a solar cell application are often deposited by plasma-based technique such as dc or rf sputtering
To calculate the surface recombination velocity (SRV), the defect density at the SiO2/Si interface (Dit), the effective total charge (Qtot) which is the sum of the charges in the SiO2 and the trapped charge at the SiO2/Si interface, and the workfunction of ITO at the ITO/SiO2 interface, are extracted by capacitance-voltage (C-V) analysis as a function of a postdeposition annealing (PDA)
The τeff decreased significantly after the ITO deposition. This suggests that some damage was induced by the reactive-plasma deposition (RPD) process and they act as recombination centers

Summary

INTRODUCTION

Indium-tin oxide (ITO) is a material widely used for optoelectronic device applications such as solar cells,[1,2] charge-coupled devices (CCDs)[3,4,5] and light emitting diodes (LEDs).[6,7] ITO films for a solar cell application are often deposited by plasma-based technique such as dc or rf sputtering. Reactive plasma deposition (RPD) is another plasma-based deposition technique to form ITO films.[12,13] This method has been reported to have the advantage of relatively-low damage by incident ions, low deposition temperature, and high growth rates,[14] a large density of interface defects (Dit) around 1012 cm-2eV-1 was produced at the SiO2/Si after the RPD of ITO, as reported in our previous work.[15]. The effects of the RPD-ITO process-induced damage on the recombination properties in the ITO/SiO2/Si structure are discussed. The values of Dit, Qtot, and the interface workfunction of ITO (φITO) are obtained by capacitancevoltage (C-V) analysis,[15] and are used for the calculation of the SRV based on the extended SRH model.[16].

Sample preparation

Qtot and Dit evaluation and SRV calculation

RESULTS AND DISCUSSION

CONCLUSIONS