Analysis of Plasma Properties and Deposition of Amorphous Silicon Alloy Solar Cells Using Very High Frequency Glow Discharge

Published

June 1, 2000

Author(s)

B Yan, J Yang, S Guha, Alan Gallagher

Abstract

Positive ionic energy distributions in modified very-high-frequency (MVHF) and radio frequency (RF) glow discharges were measured usinga retarding field analyzer. The ionic energy distribution for H₂ plasma with 75 Mhz excitation at a pressure of 0.1 torr has a peak at 22 eV with a half-width of about 6 eV. However, with 13.56 MHz excitation, the peak appears at 37 eV with a much broader half-width of 18 eV. Theintroduction of SiH₄ to the plasma shifts the distribution to lower energy. Increasing the pressure not only shifts the distribution to lower energy but also broadens the distribution. In addition, the ionic current intensity to the substrate is about five times higher for MVHF plasma than for RF plasma. In other to study the effect of ion bombardment, the deposition of a-Si alloy solar cells using MVHF was investigated in detail at different pressures and external biases. Lowering the pressure and negatively biasin the substrate increases ion bombardment energy and results in a deterioration of cell performance. It indicates that ion bombardment is not beneficial for making solar cells using MVHF. By optimizing the deposition conditions, a 10.8% initial efficiency of -Si/a-SiGe/SiGe triple-junction solar cell was achieved at a deposition rate of 0.6 nm/sec.

Proceedings Title

Amorphous and Heterogeneous Silicon Thin Films-Fundamentals to Devices, Symposium A | | Amorphous and Heterogeneous Silicon Thin Films--1999 | Materials Research Society

Volume

557

Conference Dates

April 5-9, 1999

Conference Title

Materials Research Society Symposium Proceedings

Pub Type

Conferences

Keywords

amorphous, photovoltaics, silicon

Citation

Yan, B. , Yang, J. , Guha, S. and Gallagher, A. (2000), Analysis of Plasma Properties and Deposition of Amorphous Silicon Alloy Solar Cells Using Very High Frequency Glow Discharge, Amorphous and Heterogeneous Silicon Thin Films-Fundamentals to Devices, Symposium A | | Amorphous and Heterogeneous Silicon Thin Films--1999 | Materials Research Society (Accessed December 12, 2024)