Sub-gap Photoconductivity in Germanium-silicon Films Deposited by Low Frequency Plasma

2010 ◽  
Vol 1245 ◽  
Author(s):  
Andrey Kosarev ◽  
Francisco Avila
Keyword(s):  
Photon Energy ◽  
Low Frequency ◽  
Chemical Vapor ◽  
Defect States ◽  
Constant Intensity ◽  
Characteristic Energy ◽  
Frequency Plasma ◽  
Device Applications ◽  
Si Films ◽  
Germanium Silicon

Abstract(GexSi1-x:H) films are of much interest for many device applications because of narrow band gap and compatibility with films deposited by plasma. However, electronic properties of GexSi1-x:H films for high Ge content x > 0.5 have been studied less than those of Si films. In this work, we present a study of sub-gap photoconductivity (σpc) in GexSi1-x:H films for x = 1 and x = 0.97 deposited by low frequency plasma enhanced chemical vapor deposition (LF PECVD) with both various H-dilution (RH) during growth (non-doped films) and boron (B) incorporation in the films. Spectra of sub-gap photoconductivity σpc(hν) were measured in the photon energy range of hν = 0.6 to 1.8 eV. σpc(hν) spectra were normalized to constant intensity. For hν < Eg two regions in σpc(hν) can be distinguished: “A”, where σpc is related to transitions between tail and extended states, and “B”, where photoconductivity is due to defect states. σpc(hν) in ”A” region showed exponential behavior that could be described by some characteristic energy EUPC similar to Urbach energy EU in spectral dependence of optical absorption. EUPC > EU was observed in all the films studied. This together with higher relative values (i.e. normalized by the maximum value at hν = Eg) for photoconductivity comparing with those for α means that mobility-lifetime product (μτ) depends on photon energy μτ = f(hν) that was determined from α(hν)and σpc(hν). μτ(hν) increases by factor of 20 to 40 depending on the sample with reducing hν from 1.1 to 0.7 eV. In some samples, this dependence was monotonous, while in others demonstrated maxima related to both interference and density of states. Effects of both RH and boron incorporation have been found and are discussed.

The Properties Of a-Si:H/c-Si Heterostructures Prepared By 55 kHz Pecvd For Solar Cell Application

1997 ◽  
Vol 485 ◽  
Author(s):  
B. G Budaguan ◽  
A. A. Aivazov ◽  
A. A. Sherchenkov ◽  
A. V Blrjukov ◽  
V. D. Chernomordic ◽  
...  
Keyword(s):  
Crystalline Silicon ◽  
Low Frequency ◽  
Reverse Current ◽  
Chemical Vapor ◽  
Interface State ◽  
State Density ◽  
Solar Cell Application ◽  
Current Voltage ◽  
Frequency Plasma ◽  
Device Applications

AbstractIn this work a-Si:H/c-Si heterostructures with good electronic properties of a-Si:H were prepared by 55 kHz Plasma Enhanced Chemical Vapor Deposition (PECVD). Currentvoltage and capacitance-voltage characteristics of a-Si:H/c-Si heterostructures were measuredto investigate the influence of low frequency plasma on the growing film and amorphous silicon/crystalline silicon boundary. It was established that the interface state density is low enough for device applications (<2.1010 cm−2). The current voltage measurements suggest that, when forward biased, space-charge-limited current determines the transport mechanism in a- Si:H/c-Si heterostructures, while reverse current is ascribed to the generation current in a-Si:H and c-Si depletion layers.

High-Quality A-Si Films Prepared by the Direct Photo-Cvd Method

1989 ◽  
Vol 149 ◽  
Author(s):  
S. Nakano ◽  
K. Wakisaka ◽  
M. Kameda ◽  
M. Isomura ◽  
T. Matsuyama ◽  
...  
Keyword(s):  
High Efficiency ◽  
Defect States ◽  
Low Light ◽  
High Quality ◽  
Characteristic Energy ◽  
Area Efficiency ◽  
Cvd Method ◽  
Si Solar Cell ◽  
Si Films

ABSTRACTA high-efficiency integrated-type a-Si solar cell submodule with a size of 10cm × 10cm has been fabricated and a total area efficiency of 9.6% is obtained by using a high-quality p-layer doped with B(CH3)3 We have developed an advanced direct photo-CVD method. High-quallt” a-SI films with low tail characteristic energy and low light-induced degradation is prepared by this method. We have also studied the role of Si-H2 bonds on the light-induced effect. The result implies that Si-H bonds stabilize the defect states, resulting in a large light-induced degradation.

Silicon-germanium films deposited by low-frequency plasma-enhanced chemical vapor deposition: Effect of H2 and Ar dilution

2006 ◽  
Vol 21 (1) ◽  
pp. 88-104 ◽  
Author(s):  
A. Kosarev ◽  
A. Torres ◽  
Y. Hernandez ◽  
R. Ambrosio ◽  
C. Zuniga ◽  
...  
Keyword(s):  
Chemical Vapor Deposition ◽  
Electrical Properties ◽  
Deposition Rate ◽  
Vapor Deposition ◽  
Relative Rate ◽  
Low Frequency ◽  
Chemical Vapor ◽  
Optical Measurements ◽  
Conduction Band Edge ◽  
Frequency Plasma

We have studied structure and electrical properties of Si1−YGeY:H films deposited by low-frequency plasma-enhanced chemical vapor deposition over the entire composition range from Y = 0 to Y = 1. The deposition rate of the films and their structural and electrical properties were measured for various ratios of the germane/silane feed gases and with and without dilution by Ar and by H2. Structure and composition was studied by Auger electron spectroscopy (AES), secondary ion mass spectroscopy (SIMS), and Fourier transform infrared (FTIR) spectroscopy. Surface morphology was characterized by atomic force microscopy (AFM). We found that the deposition rate increased with Y, maximizing at Y = 1 without dilution. The relative rate of Ge and Si incorporation is affected by dilution. Hydrogen preferentially bonds to silicon. Hydrogen content decreases for increasing Y. In addition, optical measurements showed that as Y goes for 0 to 1, the Fermi level moves from mid gap to the conduction band edge; i.e., the films become more n-type. No correlation was found between the pre-exponential and the activation energy of conductivity. The behavior of the conductivity γ-factor suggests a local minimum in the density of states at E ≈ 0.33 eV for the films grown with or without H-dilution and E ≈ 0.25 eV for the films with Ar dilution.

Study on Deposition of Amorphous DLC-Si Films by RF-PECVD

2013 ◽  
Vol 552 ◽  
pp. 244-247 ◽  
Author(s):  
Ji Long Tang ◽  
Jing Wang
Keyword(s):  
Refractive Index ◽  
Chemical Vapor ◽  
Test Results ◽  
Plasma Chemical ◽  
Plasma Chemical Vapor Deposition ◽  
Atomic Force ◽  
Frequency Plasma ◽  
Ft Ir ◽  
Si Films ◽  
Ft Ir Spectroscopy

In this study, we investigated DLC-Si films were deposited by PECVD from C4H10:SiH4:O2 gas mixtures. We aim to investigate the influence of hydrogen on the variation of echanical properties and microstructure of DLC-Si films synthesized by radio frequency plasma chemical vapor deposition (r.f.-PECVD). The DLC films were deposited on a silicon substrate. That the reactant gases employed in this paper are a mixture of composition. The films deposited were studied by atomic force microscope (AFM), Raman and Fourier transform infrared (FT-IR) spectroscopy. The test results show that the ratio of SiH4 in the gas mixture was successively varied to clarify its influence on the roughness, microstructure, hardness, refractive index for the DLC films. The results reveal that the increasing of the concentration of SiH4 increases sp3 ratio, refractive index and roughness. Meanwhile, increasing the SiH4 concentration causes the decrease of hardness. Finally, optic behavior is correlated to the silicon concentration for deposition with SiH4 containing reactant gas.

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