scholarly journals Sulfide and Fluoride Ions Based Passivation of GaAs(100) Surface and Concept of Combining Surface Passivation with Tunnel Junction Based Molecular Devices

2019 ◽  
Author(s):  
Pawan Tyagi
Keyword(s):  
Surface Passivation ◽  
Surface States ◽  
Single Step ◽  
Gaas Surface ◽  
Double Step ◽  
Fluoride Ions ◽  
Rutherford Back Scattering ◽  
Near Surface ◽  
Photoluminescence Study ◽  
Sulfide Ions

Sulfur interaction with GaAs can reduce the harmful effect of surface states on recombination attributes. Apart from surface passivation, study of sulfur bonding on GaAs is also important for developing novel molecular electronics and molecular spintronics devices, where a molecular channel can be connected to at least one GaAs surface via thiol functional group. Excess thiol functional groups that are not involved in making molecular device channels can serve as the passivants to quench surface states. However, the primary challenge lies in increasing the stability and effectiveness of the sulfur passivated GaAs. We have investigated the effect of single and double step surface passivation of n-GaAs(100) by using the sulfide and fluoride ions. Our single-step passivation involved the use of sulfide and fluoride ions individually. However, the two kinds of double-step passivations were performed by treating the n-GaAs surface. In the first approach GaAs surface was firstly treated with sulfide ions and secondly with fluoride ions, respectively. In the second double step approach GaAs surface was first treated with fluoride ions followed by sulfide ions, respectively. Sulfidation was conducted using the nonaqueous solution of sodium sulfide salt. Whereas the passivation steps with fluoride ion was performed with the aqueous solution of ammonium fluoride. Both sulfidation and fluoridation steps were performed either by dipping the GaAs sample in the desired ionic solution or electrochemically. Photoluminescence was conducted to characterize the relative changes in surface recombination velocity due to the single and double step surface passivation. Photoluminescence study showed that the double-step chemical treatment where GaAs was first treated with fluoride ions followed by the sulfide ions yielded the highest improvement. The time vs. photoluminescence study showed that this double-step passivation exhibited lower degradation rate as compared to widely discussed sulfide ion passivated GaAs surface. We also conducted surface elemental analysis using Rutherford Back Scattering to decipher the near surface chemical changes due to the four passivation methodologies we adopted. The double-step passivations affected the shallower region near GaAs surface as compared to the single step passivations.

scholarly journals GaAs(100) Surface Passivation with Sulfide and Fluoride Ions

MRS Advances ◽  
2017 ◽  
Vol 2 (51) ◽  
pp. 2915-2920
Author(s):  
Pawan Tyagi
Keyword(s):  
Surface Passivation ◽  
Single Step ◽  
Gaas Surface ◽  
Surface Recombination Velocity ◽  
Double Step ◽  
Fluoride Ions ◽  
Rutherford Back Scattering ◽  
Near Surface ◽  
Photoluminescence Study ◽  
Sulfide Ions

ABSTRACTInteraction of GaAs with sulfur can be immensely beneficial in reducing the deleterious effect of surface states on recombination attributes. Bonding of sulfur on GaAs is also important for developing novel molecular devices and sensors, where a molecular channel can be connected to GaAs surface via thiol functional group. However, the primary challenge lies in increasing the stability and effectiveness of the sulfur passivated GaAs. We have investigated the effect of single and double step surface passivation of n-GaAs(100) by using the sulfide and fluoride ions. Our single-step passivation involved the use of sulfide and fluoride ions individually. However, the two kinds of double-step passivations were performed by treating the n-GaAs surface. In the first approach GaAs surface was firstly treated with sulfide ions and secondly with fluoride ions, respectively. In the second double step approach GaAs surface was first treated with fluoride ions followed by sulfide ions, respectively. Sulfidation was conducted using the nonaqueous solution of sodium sulfide salt. Whereas the passivation steps with fluoride ion was performed with the aqueous solution of ammonium fluoride. Both sulfidation and fluoridation steps were performed either by dipping the GaAs sample in the desired ionic solution or electrochemically. Photoluminescence was conducted to characterize the relative changes in surface recombination velocity due to the single and double step surface passivation. Photoluminescence study showed that the double-step chemical treatment where GaAs was first treated with fluoride ions followed by the sulfide ions yielded the highest improvement. The time vs. photoluminescence study showed that this double-step passivation exhibited lower degradation rate as compared to widely discussed sulfide ion passivated GaAs surface. We also conducted surface elemental analysis using Rutherford Back Scattering to decipher the near surface chemical changes due to the four passivation methodologies we adopted. The double-step passivations affected the shallower region near GaAs surface as compared to the single step passivations.

Properties of Surface States on GaN and Related Compounds and Their Passivation by Dielectric Films

2002 ◽  
Vol 743 ◽  
Author(s):  
Hideki Hasegawa ◽  
Tamotsu Hashizume
Keyword(s):  
Plasma Treatment ◽  
Surface State ◽  
Surface Passivation ◽  
Hydrogen Plasma ◽  
Surface States ◽  
Ex Situ ◽  
Near Surface ◽  
Ecr Plasma ◽  
Good Surface ◽  
Donor States

ABSTRACTThis paper reviews the authors′ recent efforts to clarify the properties of electronic states near surfaces of GaN and AlGaN by using variousin-situandex-situcharacterization techniques, including UHV contact-less C-V, photoluminescence surface state spectroscopy (PLS3), cathode luminescence in-depth spectroscopy (CLIS),and gateless FET techniques that have been developed by the authors’ group.As a result, a model including a U-shaped surface state continuum, having a particular charge neutrality level, combined with frequent appearance of near-surface N-vacancy related deep donor states having a discrete level at Ec - 0.37eV is proposed as a unified model that can explain large gate leakage currents and current collapse in AlGaN/GaN HFETs. Hydrogen plasma treatment and SiO2deposition increase N-vacancy related deep donors. Reasonably good surface passivation can be achieved by ECR-plasma SiNx films and by ECR-plasma oxidized Al2O3films both combined with ECR N2plasma treatment.

Surface Passivation of Gaas-Based Phemt by Hydrogen Ion Irradiation

1996 ◽  
Vol 421 ◽  
Author(s):  
Song S. Shi ◽  
Ying-Lan Chang ◽  
Evelyn L. Hu ◽  
Julia J. Brown
Keyword(s):  
Quantum Wells ◽  
Leakage Current ◽  
Hall Mobility ◽  
Carrier Density ◽  
Surface Passivation ◽  
Semiconductor Device ◽  
Surface States ◽  
Hydrogen Ion ◽  
Power Performance ◽  
Near Surface

AbstractSurface passivation is a key issue in compound semiconductor device technology. The high density of surface states on unpassivated surfaces can lead to excessive non-radiative recombination at the surface, affecting optical devices, or provide leakage and low-field breakdown in electronic devices. Our previous studies on low energy, low-dose hydrogen ion treatment carried out at room temperature showed long-term improvement in the optical properties of near surface quantum wells. We have accordingly applied this process to GaAs-based pseudomorphic HEMTs (PHEMT) in order to improve their power performance. Although our process is designed so that the hydrogen reactions are confined to the surface of the substrate, a critical factor in the success of this treatment is the extent of in-diffusion of the hydrogen, and the possibility of dopant passivation. PHEMT structures were hydrogenated at various conditions and both Hall mobility and carrier density were monitored. For a low hydrogen ion dose (3 × 1016 cm−2) at 80 eV energy, some degradation of Hall mobility and carrier density was noted after the treatment, but full recovery of both parameters was achieved after a 400°C thermal anneal. Much higher hydrogen doses resulted in severe degradation of mobility and carrier density, which were only partially recovered after thermal anneal. Measurements on actual PHEMT devices showed an approximately 15% decrease in the transconductance, and in addition, a 60% decrease in the gate-to-drain leakage current after irradiation with 80 eV hydrogen ions at a dose of 3 × 1016 cm−2. The decrease of the leakage current indicates that passivation is taking place. The decrease of the transconductance suggests that hydrogen may be diffusing into the regions of the dopants. Optimization of the hydrogenation parameters should allow leakage reduction without sacrifice of transconductance.

Investigation of Surface Passivation in InAs/GaSb Strained-Layer-Superlattices Using Picosecond Excitation Correlation Measurement and Variable-Area Diode Array Surface Recombination Velocity Measurement

2005 ◽  
Vol 891 ◽  
Author(s):  
Zhimei Zhu ◽  
Elena Plis ◽  
Abdenour Amtout ◽  
Pallab Bhattacharya ◽  
Sanjay Krishna
Keyword(s):  
Infrared Detectors ◽  
Surface Passivation ◽  
Surface Recombination ◽  
Surface States ◽  
Depletion Region ◽  
Surface Recombination Velocity ◽  
Diode Array ◽  
Ammonium Sulfide ◽  
Picosecond Excitation ◽  
Recombination Velocity

ABSTRACTThe effect of ammonium sulfide passivation on InAs/GaSb superlattice infrared detectors was investigated using two complementary techniques, namely, picosecond excitation correlation (PEC) measurement and variable-area diode array (VADA) surface recombination velocity (SRV) measurement. PEC measurements were conducted on etched InAs/GaSb superlattice mesas, which were passivated in aqueous ammonium sulfide solutions of various strengths for several durations. The PEC signal's decay time constant (DTC) is proportional to carrier lifetimes. At 77 K the PEC signal's DTC of the as-grown InAs/GaSb superlattice sample was 2.0 ns, while that of the unpassivated etched sample was reduced to 1.2 ns by the surface states at the mesa sidewalls. The most effective ammonium sulfide passivation process increased the PEC signal's DTC to 10.4 ns. However it is difficult to isolate surface recombination from other processes that contribute to the lifetime using the PEC data, therefore a VADA SRV measurement was undertaken to determine the effect of passivation on surface recombination. The obtained SRV in the depletion region of the InAs/GaSb superlattice and GaSb junction was 1.1×106 cm/s for the unpassivated sample and 4.6×105 cm/s for the passivated sample. At 77 K the highest R0A value measured in our passivated devices was 2540 W cm2 versus 0.22 W cm2 for the unpassivated diodes. The results of the lifetime, the SRV and the R0A measurements indicate that ammonium sulfide passivation will improve the performance of InAs/GaSb superlattice infrared detectors.

Comparative Optical Studies of Chemically Synthesized Silicon Nanocrystals

1996 ◽  
Vol 452 ◽  
Author(s):  
Gildardo R. Delgado ◽  
Howard W.H. Lee ◽  
Susan M. Kauzlarich ◽  
Richard A. Bley
Keyword(s):  
Porous Silicon ◽  
Silicon Nanocrystals ◽  
Surface Passivation ◽  
Theoretical Calculations ◽  
Dominant Role ◽  
Blue Emission ◽  
Surface States ◽  
Si Nanocrystals ◽  
Optical And Electronic Properties ◽  
Passivation Layers

AbstractWe studied the optical and electronic properties of silicon nanocrystals derived from two distinct fabrication procedures. One technique uses a controlled chemical reaction. In the other case, silicon nanocrystals are produced by ultrasonic fracturing of porous silicon layers. We report on the photoluminescence, photoluminescence excitation, and absorption spectroscopy of various size distributions derived from these techniques. We compare the different optical properties of silicon nanocrystals made this way and contrast them with that observed in porous silicon. Our results emphasize the dominant role of surface states in these systems as manifested by the different surface passivation layers present in these different fabrication techniques. Experimental absorption measurements are compared to theoretical calculations with good agreement. Our results provide compelling evidence for quantum confinement in both types of Si nanocrystals. Our results also indicate that the blue emission from very small Si nanocrystals corresponds to the bandedge emission, while the red emission arises from traps.

Experimental Investigation of Subsonic Turbulent Flow Over Single and Double Backward Facing Steps

1962 ◽  
Vol 84 (3) ◽  
pp. 317-325 ◽  
Author(s):  
D. E. Abbott ◽  
S. J. Kline
Keyword(s):  
Experimental Investigation ◽  
Velocity Profile ◽  
Flow Pattern ◽  
Reynolds Numbers ◽  
Area Ratio ◽  
Single Step ◽  
Reattachment Length ◽  
Double Step ◽  
Wide Range ◽  
Geometric Variables

Results are presented for flow patterns over backward facing steps covering a wide range of geometric variables. Velocity profile measurements are given for both single and double steps. The stall region is shown to consist of a complex pattern involving three distinct regions. The double step contains an assymmetry for large expansions, but approaches the single-step configuration with symmetric stall regions for small values of area ratio. No effect on flow pattern or reattachment length is found for a wide range of Reynolds numbers and turbulence intensities, provided the flow is fully turbulent before the step.

Theory of shallow donor impurity near-surface states in Si and Ge

1973 ◽  
Vol 34 (1) ◽  
pp. 108-118 ◽  
Author(s):  
Vidal Emmanuel Godwin ◽  
Wayne E. Tefft
Keyword(s):  
Surface States ◽  
Shallow Donor ◽  
Donor Impurity ◽  
Near Surface

Homogenization Treatment to Optimize the Microstructures of the Al-3.5Cu-1.5Li Alloy and Analysis of Al3Zr Precipitates

2018 ◽  
Vol 921 ◽  
pp. 195-201 ◽  
Author(s):  
Jin Jun Xu ◽  
Mang Jiang
Keyword(s):  
Electron Microscopy ◽  
Scanning Electron Microscopy ◽  
Energy Dispersive Spectrometry ◽  
Single Step ◽  
Experimental Alloy ◽  
Composition Distribution ◽  
Double Step ◽  
Homogenization Treatment ◽  
Transmission Electron ◽  
Scanning Electron

The microstructure evolution and composition distribution of the cast Al-3.5Cu-1.5Li-0.11Zr alloy during single-step and double-step homogenization were studied with the help of the optical microscopy (OM), scanning electron microscopy (SEM), energy dispersive spectrometry (EDS) and transmission electron microscopy (TEM) methods. The results show that severe dendrite segregation exists in the experimental alloy. Six different homogenization treatments, conventional one-stage homogenization and double-stage homogenization are carried out, and the best homogenization treatment of the experimental alloys was achieved. Moreover, the precipitation of Al3Zr particles was significantly different after two kinds of homogenization in the experimental alloy. Compared with the single-stage homogenization, a finer particle size and distribution more diffuse of Al3Zr particles can be obtained in the double-stage homogenization treatment.

GaAs Surface Passivation for Device Applications.

1981 ◽  
Author(s):  
R. W. Grant ◽  
K. R. Elliott ◽  
S. P. Kowalczyk ◽  
D. L. Miller ◽  
J. R. Waldrop
Keyword(s):  
Surface Passivation ◽  
Gaas Surface ◽  
Device Applications

Influence of surface passivation on electric properties of individual GaAs nanowires studied by current–voltage AFM measurements

2016 ◽  
Vol 56 (2) ◽  
Author(s):  
Pavel Geydt ◽  
Prokhor A. Alekseev ◽  
Mikhail S. Dunaevskiy ◽  
Tuomas Haggrén ◽  
Joona-Pekko Kakko ◽  
...  
Keyword(s):  
Vertical Structure ◽  
Surface Passivation ◽  
Surface States ◽  
Electric Properties ◽  
Conductive Atomic Force Microscopy ◽  
Force Microscopy ◽  
Atomic Force ◽  
Gaas Nanowires ◽  
Current Voltage

Current–voltage (I–V) characteristics of vertical p-GaAs nanowires (NWs) covered by different surface passivation materials were experimentally measured by conductive atomic force microscopy (C-AFM). The obtained I–V curves for individual NWs with a diameter of 100 nm covered with AlGaAs, GaN, GaP or InP shell layers were compared to analyse the influence of surface passivation on the density of surface states and choose the most beneficial passivating material for technological applications. We have found the absence of a Schottky barrier between the golden catalytic cap on the top of a NW and the nanowire situated below and covered with an ultrathin GaP passivating layer. It was suggested that passivating material can arrange the heterostructure configuration with the GaAs NW near the Au cap. The latter mechanism was proposed to explain a strong energy barrier found in nanowires covered with InP passivation. AlGaAs passivation affected the forward threshold voltage of nanowires for NWs, which was measured simultaneously with the resistivity of each individual vertical structure from an array by means of AFM in the regime of measuring the I–V curves and onefold calculations. We made an attempt to develop the methodology of measurement and characterization of electric properties of passivated NWs.

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