The Significance of Charged Defects in Understanding the Light-Induced Degradation of Hydrogenated Amorphous Silicon-Germanium Alloys

1997 ◽  
Vol 467 ◽  
Author(s):  
Chih-Chiang Chen ◽  
Fan Zhong ◽  
J. David Cohen
Keyword(s):  
Glow Discharge ◽  
Silicon Germanium ◽  
Light Exposure ◽  
Optical Transition ◽  
Dominant Role ◽  
Hole Mobility ◽  
Thermally Induced ◽  
Device Applications ◽  
P Type ◽  
Charged Defects

ABSTRACTWe have characterized the defect state structure in a series of device quality glow discharge intrinsic, n-type doped, and p-type doped a-Si,Ge:H alloys with Ge content ranging from 20 at.% to 35 at.%. Our experimental methods include capacitance profiling, transient junction photocurrent and photocapacitance measurements. These methods have allowed us to identify one type of thermally induced defect transition plus two types of optical transitions from deep defects. Our results indicate that these transitions must involve at least two distinct defect sub-bands. Comparison of the magnitudes of these sub-bandsfor the intrinsic, n-type, and p-type alloys has allowed us to confirm that one of the optical transition belongs to D+ defect sub-band. All the optically and thermally induced bands of defect transitions are present with similar magnitudes for the most intrinsic a-Si,Ge:H alloys, which implies that charged defects play a significant role in glow discharge a-Si,Ge:H alloys. We then examined the changes in these defect densities, along with the changes in the hole mobility-lifetime products, that result from prolonged light exposure. By comparing the annealed state and light soaked state of each sample, we have been able to correlate the relative changes of the identified defect sub-band with the measured hole mobility-lifetime products. These data indicate that charged defects probably play a dominant role in determining the degradation of these a-Si,Ge:H alloys in device applications.

Effects of Light Induced Degradation on the Distribution of Deep Defects in Hydrogenated Amorphous Silicon-Germanium Alloys.

1996 ◽  
Vol 420 ◽  
Author(s):  
C. C. Chen ◽  
F. Zhong ◽  
J. D. Cohen
Keyword(s):  
Silicon Germanium ◽  
Light Exposure ◽  
Hole Mobility ◽  
Defect Band ◽  
Thermally Induced ◽  
Amorphous Silicon Germanium ◽  
Hydrogenated Amorphous ◽  
Relative Factor ◽  
Minority Carriers ◽  
Deep Defects

AbstractWe have characterized the defect state structure in a series of device quality glow discharge produced a-Si,Ge:H alloys with Ge content ranging from 30 at.% to 50 at.% using capacitance profiling, modulated photocurrent, transient junction photocurrent and photocapacitance measurements. As previously reported, these methods have allowed us to identify two types thermally induced defect transitions plus two types of optical transitions from deep defects. In the current study we have examined the changes in these defects, along with the changes in the hole mobility-time products, that result from prolonged light exposure. By comparing these changes in the annealed state and light soaked state of the same sample, we attempt to correlate the changes in defects with the hole mobility-time product. In general, although all of the defect bands are found to increase after light soaking, the relative factor is found to be different for the various defect transitions within the same sample. We also try to identify a defect bands may be acting as a “safe electron trap”, enhancing the lifetime of the minority carriers. We propose that the observed decrease of this defect band relative to the midgap defect band with light soaking could be a significant factor in determining the degradation of these a-Si, Ge:H alloys in the device performance.

scholarly journals First-Principles Study of a MoS2-PbS van der Waals Heterostructure Inspired by Naturally Occurring Merelaniite

Materials ◽  
2021 ◽  
Vol 14 (7) ◽  
pp. 1649
Author(s):  
Gemechis D. Degaga ◽  
Sumandeep Kaur ◽  
Ravindra Pandey ◽  
John A. Jaszczak
Keyword(s):  
Density Functional ◽  
Van Der Waals ◽  
Hole Mobility ◽  
Functional Theory ◽  
Mos2 Monolayer ◽  
Naturally Occurring ◽  
Weak Interlayer ◽  
Bulk Structure ◽  
P Type ◽  
Interlayer Bonding

Vertically stacked, layered van der Waals (vdW) heterostructures offer the possibility to design materials, within a range of chemistries and structures, to possess tailored properties. Inspired by the naturally occurring mineral merelaniite, this paper studies a vdW heterostructure composed of a MoS2 monolayer and a PbS bilayer, using density functional theory. A commensurate 2D heterostructure film and the corresponding 3D periodic bulk structure are compared. The results find such a heterostructure to be stable and possess p-type semiconducting characteristics. Due to the heterostructure’s weak interlayer bonding, its carrier mobility is essentially governed by the constituent layers; the hole mobility is governed by the PbS bilayer, whereas the electron mobility is governed by the MoS2 monolayer. Furthermore, we estimate the hole mobility to be relatively high (~106 cm2V−1s−1), which can be useful for ultra-fast devices at the nanoscale.

SiC Epitaxial Layers Grown by Sublimation Method and their Electrical Properties

2007 ◽  
Vol 556-557 ◽  
pp. 153-156
Author(s):  
Chi Kwon Park ◽  
Gi Sub Lee ◽  
Ju Young Lee ◽  
Myung Ok Kyun ◽  
Won Jae Lee ◽  
...  
Keyword(s):  
Electrical Properties ◽  
Epitaxial Layer ◽  
Light Emission ◽  
Epitaxial Layers ◽  
Current Voltage ◽  
Space Technique ◽  
Sublimation Method ◽  
Device Applications ◽  
P Type ◽  
Surface Morphologies

A sublimation epitaxial method, referred to as the Closed Space Technique (CST) was adopted to produce thick SiC epitaxial layers for power device applications. In this study, we aimed to systematically investigate surface morphologies and electrical properties of SiC epitaxial layers grown with varying a SiC/Al ratio in a SiC source powder during the sublimation growth using the CST method. It was confirmed that the acceptor concentration of epitaxial layer was continuously decreased with increasing the SiC/Al ratio. The blue light emission was successfully observed on a PN diode structure fabricated with the p-type SiC epitaxial layer. Furthermore, 4H-SiC MESFETs having a micron-gate length were fabricated using a lithography process and their current-voltage performances were characterized.

Low-Temperature LPCVD MEMS Technologies

2002 ◽  
Vol 729 ◽  
Author(s):  
Roger T. Howe ◽  
Tsu-Jae King
Keyword(s):  
Silicon Germanium ◽  
Polycrystalline Silicon ◽  
Rf Mems ◽  
Sige Layer ◽  
Copper Metallization ◽  
Si Films ◽  
P Type ◽  
Mems Process ◽  
Post Deposition

AbstractThis paper describes recent research on LPCVD processes for the fabrication of high-quality micro-mechanical structures on foundry CMOS wafers. In order to avoid damaging CMOS electronics with either aluminum or copper metallization, the MEMS process temperatures should be limited to a maximum of 450°C. This constraint rules out the conventional polycrystalline silicon (poly-Si) as a candidate structural material for post-CMOS integrated MEMS. Polycrystalline silicon-germanium (poly-SiGe) alloys are attractive for modular integration of MEMS with electronics, because they can be deposited at much lower temperatures than poly-Si films, yet have excellent mechanical properties. In particular, in-situ doped p-type poly-SiGe films deposit rapidly at low temperatures and have adequate conductivity without post-deposition annealing. Poly-Ge can be etched very selectively to Si, SiGe, SiO2 and Si3N4 in a heated hydrogen peroxide solution, and can therefore be used as a sacrificial material to eliminate the need to protect the CMOS electronics during the MEMS-release etch. Low-resistance contact between a structural poly-SiGe layer and an underlying CMOS metal interconnect can be accomplished by deposition of the SiGe onto a typical barrier metal exposed in contact windows. We conclude with directions for further research to develop poly-SiGe technology for integrated inertial, optical, and RF MEMS applications.

High hole mobility in boron doped diamond for power device applications

2009 ◽  
Vol 94 (9) ◽  
pp. 092102 ◽  
Author(s):  
Pierre-Nicolas Volpe ◽  
Julien Pernot ◽  
Pierre Muret ◽  
Franck Omnès
Keyword(s):  
Hole Mobility ◽  
Power Device ◽  
Boron Doped Diamond ◽  
Boron Doped ◽  
Device Applications

Si1−xGex Bulk Crystals Growth and PN Junction Formation by Diffusing Phosphorus

1999 ◽  
Vol 607 ◽  
Author(s):  
S. Kato ◽  
T. Horikoshi ◽  
T. Ohkubo ◽  
T. Iida ◽  
Y. Takano
Keyword(s):  
Silicon Germanium ◽  
Bulk Crystals ◽  
Temperature Dependent ◽  
Alloy Scattering ◽  
Self Diffusion ◽  
Pn Junction ◽  
Current Voltage ◽  
Vertical Bridgman ◽  
Current Voltage Characteristics ◽  
P Type

AbstractThe bulk crystal of silicon germanium was grown by vertical Bridgman method with germanium composition, x, varying from 0.6 to 1.0. The temperature dependent variation of the mobility is indicative of alloy scattering dominantly for the bulk wafer. Phosphorus was diffused in as-grown p-type bulk wafer at 850 °C to form pn-junction, and the diffusion coefficient of phosphorus was evaluated as a function of x. The diffusion behavior of phosphorus in silicon germanium is closely correlated with the germanium self-diffusion with changing x. For specimens with lower content x, P concentration profiles indicated “kink and tail” shape, while it was not observed for higher x. For current-voltage characteristics measurement, an ideality factor was obtained.

scholarly journals Progress on the Synthesis and Application of CuSCN Inorganic Hole Transport Material in Perovskite Solar Cells

Materials ◽  
2018 ◽  
Vol 11 (12) ◽  
pp. 2592 ◽  
Author(s):  
Funeka Matebese ◽  
Raymond Taziwa ◽  
Dorcas Mutukwa
Keyword(s):  
Solar Cells ◽  
Energy Levels ◽  
Perovskite Solar Cells ◽  
Hole Mobility ◽  
Cost Effective ◽  
Vital Role ◽  
Hole Transport ◽  
Recombination Processes ◽  
Short Synthesis ◽  
P Type

P-type wide bandgap semiconductor materials such as CuI, NiO, Cu2O and CuSCN are currently undergoing intense research as viable alternative hole transport materials (HTMs) to the spiro-OMeTAD in perovskite solar cells (PSCs). Despite 23.3% efficiency of PSCs, there are still a number of issues in addition to the toxicology of Pb such as instability and high-cost of the current HTM that needs to be urgently addressed. To that end, copper thiocyanate (CuSCN) HTMs in addition to robustness have high stability, high hole mobility, and suitable energy levels as compared to spiro-OMeTAD HTM. CuSCN HTM layer use affordable materials, require short synthesis routes, require simple synthetic techniques such as spin-coating and doctor-blading, thus offer a viable way of developing cost-effective PSCs. HTMs play a vital role in PSCs as they can enhance the performance of a device by reducing charge recombination processes. In this review paper, we report on the current progress of CuSCN HTMs that have been reported to date in PSCs. CuSCN HTMs have shown enhanced stability when exposed to weather elements as the solar devices retained their initial efficiency by a greater percentage. The efficiency reported to date is greater than 20% and has a potential of increasing, as well as maintaining thermal stability.

scholarly journals Regulation of Hole Concentration and Mobility and First-Principle Analysis of Mg-Doping in InGaN Grown by MOCVD

Materials ◽  
2021 ◽  
Vol 14 (18) ◽  
pp. 5339
Author(s):  
Lian Zhang ◽  
Rong Wang ◽  
Zhe Liu ◽  
Zhe Cheng ◽  
Xiaodong Tong ◽  
...  
Keyword(s):  
First Principles ◽  
Metalorganic Chemical Vapor Deposition ◽  
Hole Concentration ◽  
Chemical Vapor ◽  
Hole Mobility ◽  
Nitrogen Vacancy ◽  
First Principle ◽  
Mg Doping ◽  
Limiting Condition ◽  
P Type

This work studied the regulation of hole concentration and mobility in p-InGaN layers grown by metalorganic chemical vapor deposition (MOCVD) under an N-rich environment. By adjusting the growth temperature, the hole concentration can be controlled between 6 × 1017/cm3 and 3 × 1019/cm3 with adjustable hole mobility from 3 to 16 cm2/V.s. These p-InGaN layers can meet different requirements of devices for hole concentration and mobility. First-principles defect calculations indicate that the p-type doping of InGaN at the N-rich limiting condition mainly originated from Mg substituting In (MgIn). In contrast with the compensation of nitrogen vacancy in p-type InGaN grown in a Ga-rich environment, the holes in p-type InGaN grown in an N-rich environment were mainly compensated by interstitial Mg (Mgi), which has very low formation energy.

Sign in / Sign up

Export Citation Format

Share Document