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The preparation ofinsitudoped hydrogenated amorphous silicon by homogeneous chemical vapor deposition

 

作者: B. S. Meyerson,   B. A. Scott,   D. J. Wolford,  

 

期刊: Journal of Applied Physics  (AIP Available online 1983)
卷期: Volume 54, issue 3  

页码: 1461-1465

 

ISSN:0021-8979

 

年代: 1983

 

DOI:10.1063/1.332172

 

出版商: AIP

 

数据来源: AIP

 

摘要:

Raman scattering, infrared absorption, conductivity measurements, electron microprobe, and secondary ion mass spectrometry (SIMS) were used to characterize boron and phosphorus doped hydrogenated amorphous silicon (a‐Si:H) films prepared by Homogeneous Chemical Vapor Deposition (HOMOCVD). HOMOCVD is a thermal process which relies upon the gas phase pyrolysis of a source (silane containing up to 1.0% diborane or phosphine) to generate activated species for deposition upon a cooled substrate. Doped films prepared at 275 °C by this process were found to contain ∼12‐at. % hydrogen as determined by infrared absorption. We examined dopant incorporation from the gas phase, obtaining values for a distribution coefficientCD(film dopant content/gas phase dopant concentration, atomic basis) of 0.33≤CD≤0.63 for boron, while 0.4≤CD≤10.75 in the limits 3.3×10−5≤PH3/SiH4≤0.004. We interpret the data as indicative of the formation of an unstable phosphorus/silicon intermediate in the gas phase, leading to the observed enhancements inCDat high gas phase phosphine content. HOMOCVD films doped at least as efficiently as their prepared counterparts, but tended to achieve higher conductivities [&sgr;≥0.1 (&OHgr; cm)−1for 4.0% incorporated phosphorus] in the limit of heavy doping. Raman spectra showed no evidence of crystallinity in the doped films. Film properties (conductivity, activation energy of of conduction) have not saturated at the doping levels investigated here, making the attainment of higher ‘‘active’’ dopant levels a possibility. We attribute the observation that HOMOCVD appears more amenable to high ‘‘active’’ dopant levels than plasma techniques to the low (∼0.1 eV) thermal energy at which HOMOCVD proceeds, versus ∼10–100 eV for plasma techniques. Low substrate temperature (75 °C) doped films were prepared with initial results showing these films to dope as readily as those prepared at high temperature (T∼275 °C).

 

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