Browse Prior Art Database

Incorporation of Dopant Into Amorphous Silicon and Thermoelectric Device

IP.com Disclosure Number: IPCOM000052284D
Original Publication Date: 1981-May-01
Included in the Prior Art Database: 2005-Feb-11
Document File: 2 page(s) / 14K

Publishing Venue

IBM

Related People

Brodsky, MH: AUTHOR [+2]

Abstract

Dope amorphous silicon films were made from a Plasma glow discharge in a gas mixture of 1% arsenic pentafluoride (AsF(5)) and 99% silane (SiH(4)) The resulting films had several advantages over films prepared similarly using the conventional arsenic-bearing (arsine, AsH(3)) gas. The advantages are that the films from AsF(5)/SiH(4) have lower resistivity than films from AsH(3)/SiH(4) prepared under otherwise identical conditions. This indicates more efficient doping with the fluoride carrier. Films from AsF(5)/SiH(4) exhibit higher photoconductive response to about 100 mw/cm of white carriers provided 30 times more response than those made from hydride carriers. This indicates either a passivation of detrimental defects or incorporation of photosensitivity centers from the fluoride or associated impurities.

This text was extracted from a PDF file.
This is the abbreviated version, containing approximately 52% of the total text.

Page 1 of 2

Incorporation of Dopant Into Amorphous Silicon and Thermoelectric Device

Dope amorphous silicon films were made from a Plasma glow discharge in a gas mixture of 1% arsenic pentafluoride (AsF(5)) and 99% silane (SiH(4)) The resulting films had several advantages over films prepared similarly using the conventional arsenic-bearing (arsine, AsH(3)) gas. The advantages are that the films from AsF(5)/SiH(4) have lower resistivity than films from AsH(3)/SiH(4) prepared under otherwise identical conditions. This indicates more efficient doping with the fluoride carrier. Films from AsF(5)/SiH(4) exhibit higher photoconductive response to about 100 mw/cm of white carriers provided 30 times more response than those made from hydride carriers. This indicates either a passivation of detrimental defects or incorporation of photosensitivity centers from the fluoride or associated impurities. The points to notice in the table are that for each pair of samples prepared at the same substrate temperature the dark conductivities and the photoconductivities are higher when 1% AsF(5) was used instead of 1% AsH(3). The 1.2x10/-3/ Omega cm/-1/ photoconductivity is higher than any reported photoconductance for hydrogenated or hydrogenated and fluorinated amorphous silicon. It is also higher than any photoconductivity observed in this laboratory, including our most sensitive films from Si(2)H(6).

The other deposition conditions which were kept fixed for all four samples were: pressure = 0.07 torr, Gas Flow = 3.0 sccm, RF Power = 1.0 watt inductivity coupled at 13.56 MHz, fused quartz substrates, predeposited Mo contacts.

In addition to AsF there are other fluorides suitable for carriers of other commonly used copants, e.g.: PF(5), Phosphorus Pentafluoride BF(3) Boron Trifluoride which should also be useful alternatives to, e.g.: PH(3), Phosphine B2H6, Diborane which are currently used to dope a-Si:H or a-Si:H:F.

One advantage of using fluorinated dopant carrier gases rather than related hydrides is to combine in a single step the doping and the fluorination of hydrogenated amorphous silicon. Currently, fluorine is used to make a-Si:H:F by using silicon tetrafluoride, SiF(4), in combination with another gas, e.g., SiH(4) or H(2). The dopants are added by a third gas. This is a simplification o...