Pulsed Supermagnetron Plasma CVD of a-CN<sub>x</sub>:H Electron-Transport Films for Au/a-CN<sub>x</sub>:H/p-Si Photovoltaic Cells

Abstract

Hydrogenated amorphous carbon nitride (a-CN x :H) films were formed on p-Si wafers set on a lower electrode by pulsed supermagnetron plasma CVD using i-C 4 H 10 and N 2 gases. Lower electrode RF power (LORF) of 13.56 MHz (50-800 W) was modulated by a 2.5-kHz pulse at a duty ratio of 12.5%, and upper electrode RF power (UPRF) of 50-400 W was supplied continuously. The optical band gap decreased with an increase in LORF at each UPRF. The open circuit voltage of Au/a-CN x :H/p-Si photovoltaic cells (a-CN x :H film thickness: 25 nm) was about 200 mV for each cell, and the short circuit current density and energy conversion efficiency increased with LORF for each UPRF. The highest energy conversion efficiency of 0.81% was obtained at UPRF/LORF of 200/800 W.

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

“…The a-CN x :H films were deposited at a gas pressure of 4 Pa. Figure 2 shows the LORF (0 -800 W) dependence of the on-time deposition rate measured at a UPRF of 100 W. The on-time deposition rate changed a little between 200 and 400 W, being about 27 and 35 nm/min, respectively. During the off-time of LORF, the wafer temperature naturally sank below that of the wafer exposed to continuous discharge plasma [9] [23].…”

“…Gold ohmic electrodes 30-nm thick, and semitransparent in visible light were deposited for the PVCs (Figure 16 a-CN x :H thicknesses of 5 and 12.5 nm, respectively (Yamashita Denso YSS-80A with AM1.5G, 100 mW/cm 2 , calibrated by a reference Si photodiode BS-520) [36] [37]. They showed a rectifying curve in the dark, indicating the formation of a heterojunction between the a-CN x :H film and p-Si substrate [9] [10]; an a-SiC x mixed layer about 2-nm thick would be formed at the heterojunction interface [38].…”

“…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.…”

“…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].…”

Chemical vapor deposition of a-CNx:H films for electron field emission using band supermagnetron plasma

“…However, they must be deposited at high temperatures of 700−1000°C, which is too high to deposit on low-cost glass substrates [6,7]. a-CN x :H films can be deposited at temperatures below about 400°C [8,9], and show excellent electron field emission characteristics from their flat surfaces [2,[10][11][12]. For cold cathode operation of devices such as flat-panel displays and panel light sources, a large-area electron emission with a low working voltage is required.…”