The Electronic Structure, Metastability and Transport Properties of Optimized Amorphous Silicon-Germanium Alloys

1998 ◽  
Vol 507 ◽  
Author(s):  
Chih-Chiang Chen ◽  
Yoram Lubianiker ◽  
J. David Cohen ◽  
Jeffrey C. Yang ◽  
Subhendu Guha ◽  
...  
Keyword(s):  
Transport Properties ◽  
Silicon Germanium ◽  
Defect Formation ◽  
Harvard University ◽  
Defect Formation Energy ◽  
Solar Systems ◽  
Before And After ◽  
Amorphous Silicon Germanium ◽  
Defect Densities ◽  
Comprehensive Study

ABSTRACTWe have carried out a comprehensive study of the electronic properties of two series of optimized a-Si1−xGex:H alloys fabricated at United Solar Systems Corporation (“Uni-Solar”) and Harvard University, encompassing the composition range 0.2 ≤ × ≤ 1.0. Both series of samples exhibit deep defect densities that obey quite accurately the spontaneous bond-breaking model proposed by M. Stutzmann which, by considering how the defect formation energy varies with the position of Fermi energy, we have been able to extend to doped samples.We have also extended our studies to include measurements of ambipolar diffusion lengths and the effects of light-induced degradation, and thus have been able to demonstrate a direct relation between these transport properties and the measured defect levels before and after degradation.

Defect Properties of Cathode Deposited Glow Discharge Amorphous Silicon Germanium Alloys

1995 ◽  
Vol 377 ◽  
Author(s):  
Fan Zhong ◽  
Chih-Chiang Chen ◽  
J. David Cohen ◽  
Paul Wickboldt ◽  
William Paul
Keyword(s):  
Glow Discharge ◽  
Silicon Germanium ◽  
Defect Formation ◽  
Optical Spectra ◽  
Drive Level ◽  
Formation Model ◽  
Energy Distributions ◽  
Amorphous Silicon Germanium ◽  
Discharge Method ◽  
Defect Densities

ABSTRACTWe have characterized the deep defect densities and their energy distributions for a series of a-Si1-xGex:H alloys with large Ge content (0.57< × < 1.00) prepared by the cathode deposited glow discharge method. Our results indicate markedly superior properties for these samples. A small Urbach tail slope (about 45meV) was found for all samples in this alloy range. The defect densities were either obtained directly from the drive-level capacitance profiling or deduced from the sub-band-gap optical spectra. Both are substantially lower than the trend line determined from previous studies of a-Si1-xGex:H samples produced by conventional glow discharge and by Photo-CVD methods. However, the relation between the total defect densities and the optical spectra in the cathodic samples obeys the same defect formation model that has been used to successfully predict the defect densities in other types of a-Si1-xGex:H material.

Properties of amorphous silicon-germanium films and devices deposited at higher growth rates

2002 ◽  
Vol 715 ◽  
Author(s):  
Yong Liu ◽  
Vikram L. Dalal
Keyword(s):  
Amorphous Silicon ◽  
Growth Rates ◽  
Silicon Germanium ◽  
Urbach Energy ◽  
Dark Conductivity ◽  
Film Properties ◽  
Ecr Plasma ◽  
Device Properties ◽  
Amorphous Silicon Germanium ◽  
Defect Densities

AbstractWe report on the growth and properties of amorphous Silicon-Germanium [a–(Si,Ge):H] films and devices fabricated at growth rates of ∼ 5 Å/sec using a remote ECR plasma growth process. The films and devices were made using mixtures of germane and silane along with dilution with hydrogen and helium. The addition of He to the gas mixture significantly increased the growth rates. It was found that hydrogen was always necessary in order to achieve the best film and device properties. Films and devices were made across the entire bandgap range, from a-Si to a-Ge. High ratios of photo/dark conductivity and low values of Urbach energy ( > 50 meV) indicate good film properties. The defect densities were measured using space charge limited current techniques. The defect densities were in the range of 1-2 x 10 16/cm 3 –eV, about 5 times higher than for a-Si:H. Electron mobility-lifetime products were measured and found to be in the range of 2-4 x 10-7 cm2/V, even for low gap materials (1.35 eV). Single and graded gap devices were fabricated in these materials. Device fill factors of ∼ 70% were obtained in graded gap devices.

Optoelectronic Properties of Amorphous SiGec Alloys

1992 ◽  
Vol 258 ◽  
Author(s):  
J. Kolodzey ◽  
R. Schwarz ◽  
F. Wang ◽  
T. Muschik ◽  
J. Krajewski ◽  
...  
Keyword(s):  
Silicon Germanium ◽  
Plasma Deposition ◽  
Optical Gap ◽  
Random Alloy ◽  
Amorphous Si ◽  
Silicon Germanium Carbon ◽  
Amorphous Silicon Germanium ◽  
Hydrogenated Amorphous ◽  
Average Bond ◽  
Defect Densities

ABSTRACTWe describe the optoelectronic characteristics of hydrogenated amorphous silicon germanium carbon (a.Si1-x-yGexCy:H) alloys prepared by plasma deposition from SiH4/GeH4/CH4/H2 gas mixtures. a-Si1-x-yGexCy:H is a homogeneous random alloy having a variable optical gap depending on composition, with properties similar to those of amorphous Si-Ge alloys of the same optical gap but with improved thermal stability. Calculations show that if the ratio of Ge/C atomic fractions is 8.2, the average bond length matches that of unalloyed amorphous a-Si:H with the possibility of reduced defect densities at heterointerfaces. After light-soaking with high intensity white light, a sample having a 1.3 eV optical gap exhibited no Staebler-Wronski change in its properties.

Influence of Hydrogen on the Germanium Incorporation in a-Si1-xGex:H for Thin-film Solar Cell Application

2010 ◽  
Vol 1245 ◽  
Author(s):  
Chien-Ming Wang ◽  
Yen-Tang Huang ◽  
Yen Kuo-Hsi ◽  
Hung-Jung Hsu ◽  
Cheng-Hang Hsu ◽  
...  
Keyword(s):  
Thin Film ◽  
Solar Cell ◽  
Silicon Germanium ◽  
Defect Formation ◽  
Film Growth ◽  
Growth Defect ◽  
Solar Cell Application ◽  
Hydrogen Dilution ◽  
Amorphous Silicon Germanium ◽  
Analytical Tools

AbstractIn this work, we examined the Ge incorporation and the accompanied defect formation during PECVD deposition of hydrogenated amorphous silicon-germanium alloys (a-Si1-xGex:H). In particular, we studied the effect of hydrogen on film growth, defect formation, Ge and Si incorporation efficiencies, and the H-bonding configuration. Our results indicate that hydrogen has a strong effect on improving the a-Si1-xGex:H film quality and the Ge incorporation in a-Si1-xGex:H. With adequate hydrogen dilution, the a-Si1-xGex:H thin-film quality significantly improved. However, excessive hydrogen dilution degraded the film properties. A number of analytical tools were employed, including FTIR, XPS, UV-Visible spectroscopy, photoconductivity, etc. The a-Si1-xGex:H material having 24% Ge content and a bangap of 1.61ev produced the solar cell with a conversion efficiency of 7.07%.

Metastable Defects in the Amorphous Silicon-Germanium Alloys

2003 ◽  
Vol 762 ◽  
Author(s):  
J. David Cohen
Keyword(s):  
Amorphous Silicon ◽  
Silicon Germanium ◽  
Dangling Bonds ◽  
Annealing Behavior ◽  
Fundamental Properties ◽  
Silicon Materials ◽  
Salient Features ◽  
The Individual ◽  
Amorphous Silicon Germanium ◽  
Silicon Germanium Alloys

AbstractThis paper first briefly reviews a few of the early studies that established some of the salient features of light-induced degradation in a-Si,Ge:H. In particular, I discuss the fact that both Si and Ge metastable dangling bonds are involved. I then review some of the recent studies carried out by members of my laboratory concerning the details of degradation in the low Ge fraction alloys utilizing the modulated photocurrent method to monitor the individual changes in the Si and Ge deep defects. By relating the metastable creation and annealing behavior of these two types of defects, new insights into the fundamental properties of metastable defects have been obtained for amorphous silicon materials in general. I will conclude with a brief discussion of the microscopic mechanisms that may be responsible.

scholarly journals Correction: Intrinsic defect formation and the effect of transition metal doping on transport properties in a ductile thermoelectric material α-Ag2S: a first-principles study

2021 ◽  
Author(s):  
Ho Ngoc Nam ◽  
Ryo Yamada ◽  
Haruki Okumura ◽  
Tien Quang Nguyen ◽  
Katsuhiro Suzuki ◽  
...  
Keyword(s):  
Transition Metal ◽  
Transport Properties ◽  
Thermoelectric Material ◽  
First Principles ◽  
Defect Formation ◽  
Chem Phys ◽  
Intrinsic Defect ◽  
Transition Metal Doping ◽  
Metal Doping ◽  
First Principles Study

Correction for ‘Intrinsic defect formation and the effect of transition metal doping on transport properties in a ductile thermoelectric material α-Ag2S: a first-principles study’ by Ho Ngoc Nam et al., Phys. Chem. Chem. Phys., 2021, DOI: 10.1039/d0cp06624a.

Properties of Catalytic-Cvd Amorphous Silicon-Germanium (a-SiGe:H)

1990 ◽  
Vol 192 ◽  
Author(s):  
Hideki Matsumura ◽  
Masaaki Yamaguchi ◽  
Kazuo Morigaki
Keyword(s):  
Amorphous Silicon ◽  
Silicon Germanium ◽  
Hydrogenated Amorphous Silicon ◽  
Chemical Vapor ◽  
Characteristic Energy ◽  
Optical Band Gaps ◽  
Spin Resonance ◽  
Amorphous Silicon Germanium ◽  
Conductive Properties ◽  
Hydrogenated Amorphous

ABSTRACTHydrogenated amorphous silicon-germanium (a-SiGe:H) films are prepared by the catalytic chemical vapor deposition (Cat-CVD) method using a SiH4, GeH4 and H4 gas mixture. Properties of the films are investigated by the photo-thermal deflection spectroscopy (PDS) and electron spin resonance (ESR) measurements, in addition to the photo-conductive and structural studies. It is found that the characteristic energy of Urbach tail, ESR spin density and other photo-conductive properties of Cat-CVD a-SiGe:H films with optical band gaps around 1.45 eV are almost equivalent to those of the device quality glow discharge hydrogenated amorphous silicon (a-Si:H).

Investigations of Tail and Defect States in a-Si0.6Ge0.4:H Alloys by PDS and ESR - Implications for the Interaction of Weak and Dangling Bonds

1995 ◽  
Vol 377 ◽  
Author(s):  
Tilo P. Drüsedau ◽  
Andreas N. Panckow ◽  
Bernd Schröder
Keyword(s):  
Silicon Germanium ◽  
Defect Density ◽  
State Density ◽  
Model Parameters ◽  
Defect States ◽  
Conversion Model ◽  
Order Of Magnitude ◽  
Underlying Mechanisms ◽  
Amorphous Silicon Germanium ◽  
Excess Absorption

ABSTRACTInvestigations on the gap state density were performed on a variety of samples of hydrogenated amorphous silicon germanium alloys (Ge fraction around 40 at%) containing different amounts of hydrogen. From subgap absorption measurements the values of the “integrated excess absorption” and the “defect absorption” were determined. Using a calibration constant, which is well established for the determination of the defect density from the integrated excess absorption of a-Si:H and a-Ge:H, it was found that the defect density is underestimated by nearly one order of magnitude. The underlying mechanisms for this discrepancy are discussed. The calibration constants for the present alloys are determined to 8.3×1016 eV−1 cnr2 and 1.7×1016 cm−2 for the excess and defect absorption, respectively. The defect density of the films was found to depend on the Urbach energy according to the law derived from Stutzmann's dangling bond - weak bond conversion model for a-Si:H. However, the model parameters - the density of states at the onset of the exponential tails N*=27×1020 eV−1 cm−3 and the position of the demarcation energy Edb-E*=0.1 eV are considerably smaller than in a-Si:H.

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