N₂ or H₂/Isobutane Supermagnetron Plasma Chemical Vapor Deposition of Hydrogenated Amorphous CN_x Films for Application to Elementary Amorphous CN_x:H/p-Si Photovoltaic Cell

Abstract

Hydrogenated amorphous carbon nitride (a-CN x :H) films were formed on p-Si wafers set on the lower electrode by pulsed supermagnetron plasma chemical vapor deposition using N2 or H2/isobutane (i-C4H10) mixed gases. The lower-electrode rf power of 800 W (13.56 MHz) was modulated by a 2.5-kHz pulse at a duty ratio of 12.5%, and the upper-electrode rf power of 100 W was supplied continuously. The N2 or H2 gas concentration was controlled at levels of 0–80%. The optical band gap decreased with a decrease of H2 concentration and an increase of N2 concentration. For the use of these a-CN x :H films as membrane electrodes for the selective transport of photoelectrons, a-CN x :H/p-Si photovoltaic cells (PVCs) (a-CN x :H film thickness: 25 nm) were formed as prototypes. In an experiment on these PVCs, the energy conversion efficiency increased from 0.0005 (high H2) to 0.5% (high N2) with the decrease of H2 concentration and increase of N2 concentration.

Fowler-Nordheim Tunneling, Photovoltaic Applications and New Band Structure Models of Electroconductive a-CN<sub>x</sub>:H Films Formed by Supermagnetron Plasma CVD

“…However, a-CN x :H film which was fabricated by using SMP CVD has been functioned as a selective transport electrode of electrons. Hence, the film showed the charge separation of photo-generated carriers [9] [10]. The fact is that the a-CN x :H films (25 nm thickness) have shown no photoconductions under light irradiation.…”

“…Hydrogenated amorphous carbon (a-C:H) films attract interest because their properties are suited to opto-electronic and vacuum microelectronic devices, including light emission diodes, photovoltaic cells and field electron emission devices [1]- [10]. In these films, both the optical and electrical properties can be modified by nitrogen doping; i.e., they are usually regarded as hydrogenated amorphous carbon nitride (a-CN x :H) films [11]- [20].…”

“…Reduction of the wafer temperature using PRF SMP enables to use low melting substrates such as Al for the fabrication of a-CN x :H field emitters [27], because of the decreased degradation of the interface state between the substrate and the grown electroconductive a-CN x :H film. a-CN x :H films have been applied to selective transport electrodes of photoelectrons [9] [10]. Conventional silicon-or compound-semiconductor-based photovoltaic cells (PVCs) always utilize p-n junctions for the separation of photo-generated carriers, including Au/carbon material/Si PVCs [28].…”

Field Electron-Emission from a-CN<sub>x</sub>:H Films Formed on Al Films Using Supermagnetron Plasma CVD

“…As regards a high rate, extreme-density plasma such as supermagnetron plasma is preferable [14] [15]. The supermagnetron plasma becomes high-density at an rf phase difference of 180˚, which is used for sputterassisted and pulsed rf supermagnetron plasma CVD [16] [17]. Using this plasma, the high-rate and low-temperature deposition of a-CN x :H layers can be achieved.…”

“…Using the supermagnetron plasma, a-CN x :H layers with low resistivity were realized. These layers have excellent field emission characteristics [17].…”