Boron Incorporation and Its Effect on Electronic Properties of Ge:H Films Deposited by LF Plasma

2008 ◽  
Vol 1066 ◽  
Author(s):  
Andrey Kosarev ◽  
Alfonso J Torres ◽  
Nery D Checa ◽  
Yurii Kudriavtsev ◽  
Rene Asomoza ◽  
...  
Keyword(s):  
Electronic Properties ◽  
Carrier Transport ◽  
Plasma Deposition ◽  
Low Frequency ◽  
Refraction Index ◽  
Hole Transport ◽  
Localized States ◽  
Optical Measurements ◽  
Hydrogen Flow ◽  
B Doping

ABSTRACTBoron (B) doping of plasma deposited silicon films have been widely studied and applied in many devices, while B-doping of germanium has been poorly reported in literature. We have reported previously about Ge:H films with low density of localized states deposited by LF plasma with optimal hydrogen dilution.This work is devoted to a study of boron incorporation and its effect on electronic properties in Ge:H films. The films were obtained by low frequency (LF) plasma deposition from GeH4+SiH4 +B2H6 mixture diluted with hydrogen. The deposition parameters were as follow: substrate temperature Ts = 300 oC, discharge frequency f= 110 kHz, pressure P= 0.6 Torr, power W= 300 W, germane flow QGeH4= 50 sccm, silane flow, hydrogen flow QH2=3500 sccm, diborane flow was varied in the range of QB2H6=0 to 20 sccm providing boron concentration in gas phase in the range of Y=0 to 4%. Composition of the films was characterized by SIMS profiling. Hydrogen bonding was studied by FTIR. Temperature dependence of conductivity measured in DC regime in vacuum thermostat was employed to study carrier transport. Optical measurements provided optical gap, sub-gap absorption and refraction index. Boron incorporation in solid film demonstrated fast increase in the range of Y = 0 to 1.4% and then increase became slower. Hydrogen concentration in the films was determined by absorption of Ge-H stretching mode at k ≈ 1870 cm−1 and it showed weak increase with change of Y from 0 to 4%. Activation energy of conductivity increased in the range of Y = 0 to 1.5% suggesting a compensation of electron conductivity, reaching maximum value Ea =0.5 eV (corresponding approximately to Eg/2) at Y= 1.5%. Then Ea reduced to minimum value Ea = 0.27 eV at Y= 3.5% showing a trend to saturation with further Y increase. This behavior is related to change of charge transport from electron to intrinsic at Y= 1.5% and further to hole transport.

Nano-structured GeySi1-y:H Films Deposited by Low Frequency Plasma for Photovoltaic Application

2008 ◽  
Vol 1127 ◽  
Author(s):  
Andrey Kosarev ◽  
Alfonso Torres ◽  
Carlos Zuniga ◽  
Marco Adamo ◽  
Liborio Sanchez
Keyword(s):  
Electronic Properties ◽  
Urbach Energy ◽  
Low Frequency ◽  
Localized States ◽  
Statistical Parameters ◽  
Nano Structure ◽  
Mean Values ◽  
Temperature Dependence Of Conductivity ◽  
Wide Range ◽  
Grain Distribution

ABSTRACTIn this work we present the study of fabrication, Ge incorporation, structure and electronic properties of nano-structured GeySi1-y:H films with y>0.5 prepared by low frequency (LF) PECVD. GeySi1-y:H films were deposited by LF PECVD at a frequency f= 110 kHz from SiH4+GeH4+H2 gas mixture. SiH4 and GeH4 flows were varied to fabricate the films in wide range of 0<y<l. Hydrogen dilution was varied in the range of RH =20 to 80. Structure of the films was studied by AFM and SEM with consequent image processing to extract statistical parameters such as grain distribution and mean values. Composition of the films was characterized by SIMS and EDX. Electronic properties were characterized by temperature dependence of conductivity, spectral dependence of optical absorption. Sub-gap absorption was characterized by Urbach energy, EU; and defect absorption, αD. We observed grain like nano-structure with Gauss distribution of grain diameters by both AFM and SEM measurements. The most interesting films had mean grain diameter<D> = 24.0±0.7 nm, dispersion D=11.0±0.2 nm and fill factor FF=0.313, Ge content y=0.96-0.97(by SIMS and EDS). These films showed also the lowest values of Urbach energy EU = 0.030 eV and low defect absorption αD = 5×102 cm −1 (at photon energy hv = 1.04 eV) indicating on low density of localized states in mobility gap. Doped films have been also fabricated and studied. Finally we shall discuss application of the above films in photovoltaic devices.

Phosphorous and Boron Incorporation and its Effect on Optical Properties of Ge:H and Si0.01Ge0.99:HFilms Deposited by LF PECVD

2012 ◽  
Vol 1372 ◽  
Author(s):  
Nery Delgadillo ◽  
Andrey Kosarev ◽  
Afonso Torres ◽  
Lancelot Garcia ◽  
Brian Gonzales
Keyword(s):  
Gas Phase ◽  
Secondary Ion Mass Spectrometry ◽  
Solid Phase ◽  
Chemical Vapour ◽  
Low Frequency ◽  
Localized States ◽  
Optical Measurements ◽  
Band Tail ◽  
Frequency Plasma ◽  
Secondary Ion

ABSTRACTDeposition conditions that provided low absorption related to both band tail and deep localized states have been found for both materials Ge:H and Si1YGeY:H. Phosphorous incorporation on Si0.01Ge0.99:H films and boron incorporation on Ge:H films were deposited by low frequency plasma-enhanced chemical vapour deposition (LF PECVD). The phosphorous incorporation in solidphase was observed to preferential with the increase of the doping in the gas phase to 2.5 %, and 2.5% to 4% was observed preferential Si0.01Ge0.99 film, boron incorporation in solid phase increase linearly with the increase of the doping gas phase. The content of solid phase was characterized by Secondary ion mass spectrometry (SIMS) profiling. Hydrogen concentration in the films was determined from Fourier transform infrared spectroscopy (FTIR) and SIMS measurements. Optical measurements provided optical gap, localized states, and band tail. A significant reduction of both band tail and deep localized states were observed at boron incorporation in solid phase = 0.004% on Ge:H films and the same were observed at phosphorous incorporation in solid phase = 0.29% on Si0.01Ge0.99:H films.

scholarly journals Charge Sharing and Charge Loss in High-Flux Capable Pixelated CdZnTe Detectors

Sensors ◽  
2021 ◽  
Vol 21 (9) ◽  
pp. 3260
Author(s):  
Kjell A. L. Koch-Mehrin ◽  
Sarah L. Bugby ◽  
John E. Lees ◽  
Matthew C. Veale ◽  
Matthew D. Wilson
Keyword(s):  
Carrier Transport ◽  
Hole Transport ◽  
Uniform Electric Field ◽  
Photon Flux ◽  
High Flux ◽  
Charge Sharing ◽  
Cdte Detector ◽  
Charge Loss ◽  
Cdznte Detectors ◽  
Detector Model

Cadmium zinc telluride (CdZnTe) detectors are known to suffer from polarization effects under high photon flux due to poor hole transport in the crystal material. This has led to the development of a high-flux capable CdZnTe material (HF-CdZnTe). Detectors with the HF-CdZnTe material have shown promising results at mitigating the onset of the polarization phenomenon, likely linked to improved crystal quality and hole carrier transport. Better hole transport will have an impact on charge collection, particularly in pixelated detector designs and thick sensors (>1 mm). In this paper, the presence of charge sharing and the magnitude of charge loss were calculated for a 2 mm thick pixelated HF-CdZnTe detector with 250 μm pixel pitch and 25 μm pixel gaps, bonded to the STFC HEXITEC ASIC. Results are compared with a CdTe detector as a reference point and supported with simulations from a Monte-Carlo detector model. Charge sharing events showed minimal charge loss in the HF-CdZnTe, resulting in a spectral resolution of 1.63 ± 0.08 keV Full Width at Half Maximum (FWHM) for bipixel charge sharing events at 59.5 keV. Depth of interaction effects were shown to influence charge loss in shared events. The performance is discussed in relation to the improved hole transport of HF-CdZnTe and comparison with simulated results provided evidence of a uniform electric field.

Analysis of low frequency noise characteristics in p-type polycrystalline silicon thin film transistors

2017 ◽  
Vol 31 (19-21) ◽  
pp. 1740020
Author(s):  
Yuan Liu ◽  
Yun-Fei En ◽  
Wen-Xiao Fang
Keyword(s):  
Thin Film ◽  
Thin Film Transistors ◽  
Polycrystalline Silicon ◽  
Low Frequency ◽  
Gate Oxide ◽  
Localized States ◽  
Frequency Noise ◽  
Silicon Thin Film ◽  
Noise Characteristics ◽  
P Type

Low frequency noises in the p-type polycrystalline silicon thin film transistors are investigated. It shows a pure 1/f[Formula: see text] (with [Formula: see text] near one) noise behavior which can be explained by emission and trapping processes of carriers between trapping states. Subsequently, the gate voltage-dependent drain current noise power spectral densities closely follow the mobility fluctuation model, and the average Hooge’s parameter is then extracted. By considering traditional tunneling processes, the flat-band voltage spectral density is extracted and the concentration of traps in the grain boundary is calculated to be [Formula: see text]. By converting the frequency to tunneling depth of carriers in the gate oxide, the spatial distribution of gate oxide trapped charges are obtained. Finally, the distribution of localized states in the energy band is extracted. The experimental results show an exponential deep states and tail states distribution in the band gap while [Formula: see text] is about [Formula: see text], [Formula: see text] is [Formula: see text][Formula: see text]617 K, [Formula: see text] is [Formula: see text] and [Formula: see text] is [Formula: see text][Formula: see text]265 K.

Comparison of Doping of Gey Si1-y:H (y>0.95) Films Deposited by Low Frequency PECVD at High (300°C) and Low (160°C) Temperatures

2012 ◽  
Vol 1426 ◽  
pp. 295-299
Author(s):  
Ismael Cosme ◽  
Andrey Kosarev ◽  
Francisco Temoltzi Avila ◽  
Adrian Itzmoyotl
Keyword(s):  
Activation Energy ◽  
Deposition Temperature ◽  
Solid Phase ◽  
Low Frequency ◽  
General Effect ◽  
Temperature Conductivity ◽  
Room Temperature Conductivity ◽  
High Deposition Temperature ◽  
B Doping ◽  
Low Deposition Temperature

ABSTRACTIn this work we present the results of comparative study n- and p-doping of Ge:H and Ge0.96Si0.04 :H films deposited by LF PECVD at high deposition temperature (HT) Td=300°C and low deposition temperature (LT) Td=160°C. The concentration of boron and phosphorus in solid phase was measured by means of SIMS technique. Such parameters as spectral dependence of absorption coefficient, room temperature conductivity σRT and activation energy Ea for both intrinsic and doped films were obtained. The doping range studied in gas phase was for boron [B]gas= 0 to 0.15% and for phosphorus [P]gas= 0 to 0.2%. In general effect of deposition temperature on P and B doping has been demonstrated. For LT films changes of [P]gas=0.04% to 0.22% resulted in more than 2 orders increasing conductivity and reducing activation energy from Ea=0.28 to 0.16 eV. HT films in the range of [P]gas=0.04% to 0.2% demonstrated saturation of conductivity. HT films showed continuous reducing Ea with increase of [P]gas. In the case of boron doping both HT and LT films had a minimum of conductivity at certain values of [B]gas=0.05% (LT films) and 0.04% (HT films) and related maximums of activation energy Ea(max) at the same doping with Ea(max)=0.47 eV for HT and Ea(max)=0.53 eV for LT films. It suggests a compensation of electron conductivity in un-doped films for low B doping. Further raising [B]gas leads to reducing Ea and the smallest Ea=0.27 eV was obtained at [B]gas=0.18% for HT films and Ea=0.33 eV at [B]gas=0.14% for LH films.

Low frequency plasma deposition and characterization of Si1−xGex:H,F films

2004 ◽  
Vol 338-340 ◽  
pp. 91-96 ◽  
Author(s):  
R. Ambrosio ◽  
A. Torres ◽  
A. Kosarev ◽  
A. Ilinski ◽  
C. Zúñiga ◽  
...  
Keyword(s):  
Plasma Deposition ◽  
Low Frequency ◽  
Frequency Plasma

Manifestation of Carrier Relaxation Through the Manifold of Localized States in PCDTBT:PC60BM Bulk Heterojunction Material: The Role of PC84BM Traps on the Carrier Transport

2012 ◽  
Vol 24 (17) ◽  
pp. 2273-2277 ◽  
Author(s):  
Wei Lin Leong ◽  
Gerardo Hernandez-Sosa ◽  
Sarah R. Cowan ◽  
Daniel Moses ◽  
Alan J. Heeger
Keyword(s):  
Carrier Transport ◽  
Bulk Heterojunction ◽  
Localized States ◽  
Carrier Relaxation

Cytochemische Untersuchungen zur Reproduktion des Tabakmosaikvirus

1961 ◽  
Vol 16 (8) ◽  
pp. 520-538 ◽  
Author(s):  
Hendrik Zech
Keyword(s):  
Electric Fields ◽  
Uv Light ◽  
Refraction Index ◽  
Optical Measurements ◽  
Uv Spectrophotometry ◽  
X Rays ◽  
Optical Absorbance ◽  
Wide Range ◽  
Light Losses

Crystalline or paracrystalline tobacco mosaic virus (TMV) inclusions are known to be composed mainly of densely packed TMV-rods. These inclusions were studied in situ within infected tobacco leaf hair cells by scanning UV-microspectrophotometry. Comparative measurements in the macroand micro ranges of the instruments were carried out on purified TMV at low and high concentrations, on its separated and reconstituted RNA and protein parts and on isolated TMV-crystals, to permit the interpretation of the optical properties of TMV inclusions in situ. The optical absorbance of TMV in solution and in dried concentrates at room temperature could in part be attributed to distribution inhomogeneities caused by local particle aggregations being oriented to differing degrees. The resulting non-uniform electric fields around and within such unevenly distributed particle complexes caused local jumps of the refraction index and thereby unspecific light losses, chiefly through scattering. The apparent deviation from Beers law was found to be greatest at particle concentrations of 1 - 2 per cent. At higher concentrations the contribution of scatter to light losses was found to decrease again, probably because of increasing order of particles within the aggregates. On the other hand the specific absorbance of the chromophores of TMV over a wide range of concentration was not affected to a measurable degree by changing the distances between the rods. There was no indication that the charged groups of the RNA-cores within intact particles interacted with charged groups of other particles however great their proximity. The ribose phosphate backbone of the RNA strand, deeply embedded within the protein helix, may account for this phenomenon. However, isolated TMV-RNA reacted strongly to changes of the surrounding electric fields when concentrations were varied, and showed pronounced hypochromicity at higher concentrations and following prolonged irridation by x-rays and UV-light. RNA in dried and irradiated droplets was characterized by up to 55% lower extinction coefficients than freshly prepared RNA in solution. The hyprochromic effects caused by irradiation were shown to be almost, but not completely reversible. Hypochromicity increased towards the shorter wavelengths, diminishing the ratio E260/E280 from about 2.0 for diluted RNA to 1.4 for concentrated specimens. Mixing TMV-protein subunits with RNA before drying, leading to partial reconstitution of TMV particles, diminished the hypochromic effect resulting from irradiation of the concentrate. High UV-radiation doses applied to concentrated TMV solutions led to a marked splitting of RNA from protein, as revealed by UV-spectrophotometry of the supernatants and pellets of centrifuged irradiated specimens. Model measurements of intracellular and subsequently isolated TMV crystals combined with empirically derived parameters led to the construction of a correction curve, permitting interpretations of optical measurements on in situ TMV inclusion bodies.

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