Structure and Optoelectronic Properties as a Function of Hydrogen Dilution of Micro-Crystalline Silicon Films Prepared by Hot Wire Chemical Vapor Deposition

1999 ◽  
Vol 557 ◽  
Author(s):  
Guozhen Yue ◽  
Jing Lin ◽  
Qi Wang ◽  
Daxing Han
Keyword(s):  
Crystalline Silicon ◽  
Chemical Vapor ◽  
Peak Position ◽  
Initial Growth ◽  
Hot Wire ◽  
Dilution Ratio ◽  
Structure Transition ◽  
Transparent Substrate ◽  
Hydrogen Dilution ◽  
Substrate Side

AbstractFilms prepared by hot wire CVD using H dilution ratio, R=H 2/SiH4, from 1 to 20 were studied by X-ray, Raman, PL, and conductivity measurements. We found that (a) when the dilution ratio reached R=3, the structure transition from amorphous to microcrystalline growth occured; meanwhile, PL spectrum showed a dual-peak at 1.3 and 1.0 eV; (b) the total intensity, band width, and peak position of the low energy PL band decreased with increasing H dilution; (c) both the Raman and PL measured from the transparent substrate side showed that initial growth tends to be amorphous and a portion of μc-Si was formed when R ≥ 5; and (d) the conductivity activation energy first decreased from 0.68 to 0.15 eV when the film transition from a- to μc-Si; then increased slightly with increasing μc-Si fraction. The results demonstrate that the variation of the H-dilution ratio has significant effects on both the film structures and the optoelectric properties.

Increase of Hydrogen-Radical Density and Improvement of The Crystalline Volume Fraction of Microcrystalline Silicon Films Prepared by Hot-Wire Assisted Pecvd Method

2000 ◽  
Vol 609 ◽  
Author(s):  
Norimitsu Yoshida ◽  
Takashi Itoh ◽  
Hiroki Inouchi ◽  
Hidekuni Harada ◽  
Katsuhiko Inagaki ◽  
...  
Keyword(s):  
Volume Fraction ◽  
Chemical Vapor ◽  
Rf Plasma ◽  
Hot Wire ◽  
Dilution Ratio ◽  
Microcrystalline Silicon ◽  
Hydrogen Dilution ◽  
Hydrogen Radical ◽  
Hydrogen Radicals ◽  
Hydrogenated Amorphous

ABSTRACTHigher crystalline Si volume fractions in hydrogenated microcrystalline silicon ( µc-Si:H) films have been achieved by the hot-wire assisted plasma enhanced chemical vapor deposition (HWA-PECVD) method compared with those in films by conventional PECVD. µc-Si:H films can also be prepared by HWA-PECVD under typical conditions used for preparing hydrogenated amorphous silicon (a-Si:H) films by PECVD, in which the hydrogen-dilution ratio (H2 / SiH4) is ∼ 10. The hot wire seems to produce hydrogen radicals. As a result, the HWA- PECVD method can control hydrogen-radical densities in the RF plasma, and this method can also control the ratio of hydrogen coverage at the surface of the film.

Characterization of Microcrystalline Transition from Amorphous Silicon as a Function of Hydrogen Dilution and Substrate Temperature of Hot-wire CVD

2002 ◽  
Vol 715 ◽  
Author(s):  
Keda Wang ◽  
Haoyue Zhang ◽  
Jian Zhang ◽  
Jessica M. Owens ◽  
Jennifer Weinberg-Wolf ◽  
...  
Keyword(s):  
Substrate Temperature ◽  
Sudden Change ◽  
Chemical Vapor ◽  
Threshold Value ◽  
Ir Absorption ◽  
Sudden Increase ◽  
Hot Wire ◽  
Hydrogen Dilution ◽  
Integral Absorption ◽  
Two Peaks

Abstracta-Si:H films were prepared by hot wire chemical vapor deposition. One group was deposited at a substrate temperature of Ts=250°C with varied hydrogen-dilution ratio, 0<R<10; the other group was deposited with fixed R=3 but a varied Ts from 150 to 550°C. IR, Raman and PL spectra were studied. The Raman results indicate that there is a threshold value for the microstructure transition from a- to μc-Si. The threshold is found to be R ≈ 2 at Ts = 250°C and Ts ≈ 200°C at R=3. The IR absorption of Si-H at 640 cm-1 was used to calculate the hydrogen content, CH. CH decreased monotonically when either R or Ts increased. The Si-H stretching mode contains two peaks at 2000 and 2090 cm-1. The ratio of the integral absorption peaks I2090/(I2090+I2090) showed a sudden increase at the threshold of microcrystallinity. At the same threshold, the PL features also indicate a sudden change from a- to μc-Si., i.e. the low energy PL band becomes dominant and the PL total intensity decreases. We attribute the above IR and PL changes to the contribution of microcrystallinity, especially the c-Si gain-boundaries.

scholarly journals Comparison Study of a-SiGe Solar Cells and Materials Deposited Using Different Hydrogen Dilution

2000 ◽  
Vol 609 ◽  
Author(s):  
H. Povolny ◽  
P. Agarwal ◽  
S. Han ◽  
X. Deng
Keyword(s):  
Stainless Steel ◽  
Solar Cells ◽  
Crystalline Silicon ◽  
Single Layer ◽  
Chemical Vapor ◽  
Hydrogen Dilution ◽  
Current Voltage ◽  
Ir Transmission ◽  
Cell Current ◽  
Steel Substrates

ABSTRACTA-SiGe n-i-p solar cells with i-layer deposited via plasma enhanced chemical vapor deposition (PECVD) with a germane to disilane ratio of 0.72 and hydrogen dilution R=(H2 flow)/(GeH4+Si2H6 flow) values of 1.7, 10, 30, 50, 120, 180 and 240 were deposited on stainless steel substrates. This germane to disilane ratio is what we typically use for the i-layer in the bottom cell of our standard triple-junction solar cells. Solar cell current-voltage curves (J-V) and quantum efficiency (QE) were measured for these devices. Light soaking tests were performed for these devices under 1 sun light intensity at 50° C. While device with R=30 showed the highest initial efficiency, the device with R=120 exhibit higher stabilized efficiency after 1000 hours of light soaking.Single-layer a-SiGe films (∼500 nm thick) were deposited under the same conditions as the i-layer of these devices on a variety of substrates including 7059 glass, crystalline silicon, and stainless steel for visible-IR transmission spectroscopy, FTIR, and hydrogen effusion studies. It is interesting to note 1) the H content in the film decreased with increasing R based on both the IR and H effusion measurements, and 2) while the H content changes significantly with different R, the change in Eg is relatively small. This is most likely due to a change in Ge content in the film for different R.

Performances of Nano/Amorphous Silicon Films Produced by Hot Wire Plasma Assisted Technique

1998 ◽  
Vol 507 ◽  
Author(s):  
I. Ferreira ◽  
H. Águas ◽  
L. Mendes ◽  
F. Fernandes ◽  
E. Fortunato ◽  
...  
Keyword(s):  
Amorphous Silicon ◽  
Transport Properties ◽  
Oxygen Content ◽  
Hydrogen Content ◽  
Crystalline Silicon ◽  
Silicon Films ◽  
Hot Wire ◽  
Hydrogen Dilution ◽  
Nano Crystalline ◽  
Doped Silicon

ABSTRACTThis work reports on the performances of undoped and n doped amorphous/nano-crystalline silicon films grown by hot wire plasma assisted technique. The film's structure (including the presence of several nanoparticles with sizes ranging from 5 nm to 50 nm), the composition (oxygen and hydrogen content) and the transport properties are highly dependent on the filament temperature and on the hydrogen dilution. The undoped films grown under low r.f. power (≍ 4 mWcm−2) and with filament temperatures around 1850 °K have dark conductivities below 10−1Scm−1, optical gaps of about 1.5 eV and photo-sensitivities above 105, (under AM3.5), with almost no traces of oxygen content. N- doped silicon films were also fabricated under the same conditions which attained conductivities of about 10−2Scm−1.

Thin Film a-Si/poly-Si Multibandgap Tandem Solar Cells With Both Absorber Layers Deposited by Hot Wire Cvd

2001 ◽  
Vol 664 ◽  
Author(s):  
R.E.I. Schropp ◽  
C.H.M. Van Der Werf ◽  
M.K. Van Veen ◽  
P.A.T.T. Van Veenendaal ◽  
R. Jimenez Zambrano ◽  
...  
Keyword(s):  
Solar Cells ◽  
Substrate Temperature ◽  
Band Gap ◽  
Steel Substrate ◽  
Light Trapping ◽  
Chemical Vapor ◽  
Hot Wire ◽  
Tandem Solar Cells ◽  
Hydrogen Dilution ◽  
P Type

ABSTRACTThe first competitive a-Si/poly-Si multibandgap tandem cells have been made in which the two intrinsic absorber layers are deposited by Hot Wire Chemical Vapor Deposition (HWCVD). These cells consist of two stacked n-i-p type solar cells on a plain stainless steel substrate using plasma deposited n- and p-type doped layers and Hot-Wire deposited intrinsic (i) layers, where the i-layer is either amorphous (band gap 1.8 eV) or polycrystalline (band gap 1.1 eV). In this tandem configuration, all doped layers are microcrystalline and the two intrinsic layers are made by decomposing mixtures of silane and hydrogen at hot filaments in the vicinity of the substrate. For the two layers we used individually optimized parameters, such as gas pressure, hydrogen dilution ratio, substrate temperature, filament temperature, and filament material. The solar cells do not comprise an enhanced back reflector, but feature a natural mechanism for light trapping, due to the texture of the (220) oriented poly-Si absorber layer and the fact that all subsequent layers are deposited conformally. The deposition rate for the throughput limiting step, the poly-Si i-layer, is ≍ 5-6 Å/s. This layer also determines the highest substrate temperature required during the preparation of these tandem cells (500 °C). The initial efficiency obtained for these tandem cells is 8.1 %. The total thickness of the silicon nip/nip structure is only 1.1 µm.

scholarly journals Depth-dependent crystallinity of nano-crystalline silicon induced by step-wise variation of hydrogen dilution during hot-wire CVD

2015 ◽  
Vol 619 ◽  
pp. 012002
Author(s):  
C J Arendse ◽  
B A van Heerden ◽  
T F G Muller ◽  
F R Cummings ◽  
C J Oliphant ◽  
...  
Keyword(s):  
Crystalline Silicon ◽  
Hot Wire ◽  
Hydrogen Dilution ◽  
Nano Crystalline
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