Hydrogenated amorphous silicon deposited at very high growth rates by an expanding Ar–H2–SiH4 plasma

Abstract

The properties of hydrogenated amorphous silicon (a-Si:H) deposited at very high growth rates (6–80 nm/s) by means of a remote Ar–H2–SiH4 plasma have been investigated as a function of the H2 flow in the Ar–H2 operated plasma source. Both the structural and optoelectronic properties of the films improve with increasing H2 flow, and a-Si:H suitable for the application in solar cells has been obtained at deposition rates of 10 nm/s for high H2 flows and a substrate temperature of 400 °C. The “optimized” material has a hole drift mobility which is about a factor of 10 higher than for standard a-Si:H. The electron drift mobility, however, is slightly lower than for standard a-Si:H. Furthermore, preliminary results on solar cells with intrinsic a-Si:H deposited at 7 nm/s are presented. Relating the film properties to the SiH4 dissociation reactions reveals that optimum film quality is obtained for conditions where H from the plasma source governs SiH4 dissociation and where SiH3 contributes dominantly to film growth. Conditions where ion-induced dissociation reactions of SiH4 prevail and where the contribution of SiH3 to film growth is much smaller lead to inferior film properties. A large contribution of very reactive (poly)silane radicals is suggested as the reason for this inferior film quality. Furthermore, a comparison with film properties and process conditions of other a-Si:H deposition techniques is presented.

Improved conductivity of aluminum-doped ZnO: The effect of hydrogen diffusion from a hydrogenated amorphous silicon capping layer

“…More details were reported elsewhere. 24,25 As a next step, an SPC process for 10 h at 600 C in vacuum (P ¼ 10 À4 Pa) was performed to fully crystallize a-Si:H. The heating rate was programmed as follows: 10 deg/min from room temperature to 400 C followed by 1 deg/min in the range of 400-600 C and 10 h at 600 C. Afterwards, the power of the heater was switched off to let the samples cool down to room temperature.…”

Population inversion in a magnetized hydrogen plasma expansion as a consequence of the molecular mutual neutralization process

“…For instance, atomic hydrogen radicals serve as primary reactive particles for surface modification or thin-film deposition [1,2]. For fusion plasma heating, one of the main research challenges is to develop efficient negative ion sources.…”

High-Quality Surface Passivation Obtained by High-Rate Deposited Silicon Nitride, Silicon Dioxide and Amorphous Silicon using the Versatile Expanding Thermal Plasma Technique

“…Hydrogenated amorphous silicon deposited by the ETP technique is already studied in great detail for the application in thin film solar cells [14]. Using the ETP technique with an Ar-H2-SiH4 mixture, it was shown that device quality material could be deposited at a deposition rate of 10 nm/s [14].…”

“…Using the ETP technique with an Ar-H2-SiH4 mixture, it was shown that device quality material could be deposited at a deposition rate of 10 nm/s [14]. Recently, amorphous silicon has also attracted interest from the crystalline silicon solar cell community due to its excellent surface passivation on …”