Optical and electrical study of cap layer effect in QHE devices with double-2DEG

2013 ◽  
Vol 1617 ◽  
pp. 31-36 ◽  
Author(s):  
L. Zamora-Peredo ◽  
I. Cortes-Mestizo ◽  
L. García-Gonzáez ◽  
J. Hernández-Torres ◽  
T. Hernandez-Quiroz ◽  
...  
Keyword(s):  
Electric Field ◽  
Room Temperature ◽  
Quantum Hall ◽  
Three Samples ◽  
Cap Layer ◽  
Layer Effect ◽  
Hall Effect Measurements ◽  
Band Profile ◽  
Surface Electric Field ◽  
Dimensional Electron Gas

ABSTRACTIn this work we report on the characteristics of GaAs/AlGaAs heterostructures with a symmetric double two-dimensional electron gas (D-2DEG). Optical characterization was made by room temperature photoreflectance (PR) spectroscopy as well as electrical properties were determinated using the quantum Hall effect measurements at 2K. In order to study the surface effects on the conduction band profile, three samples with different GaAs cap layer thickness (25, 60 and 80 nm) were grown by the molecular beam epitaxy. Photoreflectance spectra at room temperature show the wide-period Franz-Keldysh oscillations between 1.42 and 1.70 eV originated by the surface electric field. The analysis of these oscillations shows that the surface electric field varies from 503 to 120 kV/cm whereas the thickness of the cap layer increases that was produced by the reduction of the depletion zone near the surface. Using QHE measurements we found that electron density increases if the surface electric field decreases.

Effects of surface electric field on SnO 2 room temperature gas sensors fabricated on nanospike substrates

2012 ◽  
Author(s):  
Haizhou Ren ◽  
Pengtao Wang ◽  
Haibin Huo ◽  
Mengyan Shen ◽  
Marina Ruths ◽  
...  
Keyword(s):  
Electric Field ◽  
Gas Sensors ◽  
Room Temperature ◽  
Surface Electric Field

scholarly journals Photoreflectance and Raman Study of Surface Electric States on AlGaAs/GaAs Heterostructures

2016 ◽  
Vol 2016 ◽  
pp. 1-8
Author(s):  
Luis Zamora-Peredo ◽  
Leandro García-González ◽  
Julián Hernández-Torres ◽  
Irving E. Cortes-Mestizo ◽  
Víctor H. Méndez-García ◽  
...  
Keyword(s):  
Electric Field ◽  
Penetration Depth ◽  
Layer Thickness ◽  
Surface Passivation ◽  
Electronic States ◽  
Cap Layer ◽  
Raman Study ◽  
Surface Electric Field ◽  
532 Nm ◽  
Good Agreement

Photoreflectance (PR) and Raman are two very useful spectroscopy techniques that usually are used to know the surface electronic states in GaAs-based semiconductor devices. However, although they are exceptional tools there are few reports where both techniques were used in these kinds of devices. In this work, the surface electronic states on AlGaAs/GaAs heterostructures were studied in order to identify the effect of factors like laser penetration depth, cap layer thickness, and surface passivation over PR and Raman spectra. PR measurements were performed alternately with two lasers (532 nm and 375 nm wavelength) as the modulation sources in order to identify internal and surface features. The surface electric field calculated by PR analysis decreased whereas the GaAs cap layer thickness increased, in good agreement with a similar behavior observed in Raman measurements (IL-/ILOratio). When the heterostructures were treated by Si-flux, these techniques showed contrary behaviors. PR analysis revealed a diminution in the surface electric field due to a passivation process whereas theIL-/ILOratio did not present the same behavior because it was dominated by the depletion layers width (cap layer thickness) and the laser penetration depth.

Variations in the photoconductivity and in the electrical counting properties of diamonds

1956 ◽  
Vol 234 (1198) ◽  
pp. 419-432 ◽  
Keyword(s):  
Electrical Conductivity ◽  
Electric Field ◽  
Hall Effect ◽  
Temperature Effects ◽  
Room Temperature ◽  
Red Light ◽  
Quantitative Relationship ◽  
Charge Carriers ◽  
Light Irradiation ◽  
Hall Effect Measurements

The electrical conductivity produced by β -ray bombardment and by light irradiation in several diamonds was investigated in the temperature range 150 to 500° K. Considerable uniformity was observed in the behaviour of the specimens; all of them polarized strongly in the dark at room temperature, and polarization could be effectively eliminated by pulsing the electric field while maintaining the β -flux. Both the counting response and the photoconductivity increased as the temperature was lowered. This was interpreted as being largely due to an increase in the mobility of the charge carriers at lower temperatures, the quantitative relationship being consistent with Hall effect measurements. Accumulation of polarization was reduced by irradiation with red light or by elevation of temperature; at 420° K little sign of polarization remained. From various temperature effects, the thermal depths of the trapping levels in these diamonds were estimated at 0⋅6, 0⋅8 and 1 eV.

The Effect of Roughness Features on Mos Surface Electric Field and Fowler-Nordheim Tunneling Behavior

1997 ◽  
Vol 473 ◽  
Author(s):  
Heng-Chih Lin ◽  
Edwin C. Kan ◽  
Toshiaki Yamanaka ◽  
Simon J. Fang ◽  
Kwame N. Eason ◽  
...  
Keyword(s):  
Electric Field ◽  
Three Dimensional ◽  
Tunneling Current ◽  
Gate Oxide ◽  
Oxide Thickness ◽  
Interface Roughness ◽  
Normal Electric Field ◽  
Surface Electric Field ◽  
Tunneling Behavior ◽  
Nordheim Tunneling

ABSTRACTFor future CMOS GSI technology, Si/SiO2 interface micro-roughness becomes a non-negligible problem. Interface roughness causes fluctuations of the surface normal electric field, which, in turn, change the gate oxide Fowler-Nordheim tunneling behavior. In this research, we used a simple two-spheres model and a three-dimensional Laplace solver to simulate the electric field and the tunneling current in the oxide region. Our results show that both quantities are strong functions of roughness spatial wavelength, associated amplitude, and oxide thickness. We found that RMS roughness itself cannot fully characterize surface roughness and that roughness has a larger effect for thicker oxide in terms of surface electric field and tunneling behavior.

scholarly journals Investigations on the Optical Properties of InGaN/GaN Multiple Quantum Wells with Varying GaN Cap Layer Thickness

2020 ◽  
Vol 15 (1) ◽  
Author(s):  
Xiaowei Wang ◽  
Feng Liang ◽  
Degang Zhao ◽  
Zongshun Liu ◽  
Jianjun Zhu ◽  
...  
Keyword(s):  
Optical Properties ◽  
Quantum Wells ◽  
Layer Thickness ◽  
Stark Effect ◽  
Chemical Vapor ◽  
Multiple Quantum ◽  
Three Samples ◽  
Measurement Results ◽  
Cap Layer ◽  
The Difference

Abstract Three InGaN/GaN MQWs samples with varying GaN cap layer thickness were grown by metalorganic chemical vapor deposition (MOCVD) to investigate the optical properties. We found that a thicker cap layer is more effective in preventing the evaporation of the In composition in the InGaN quantum well layer. Furthermore, the quantum-confined Stark effect (QCSE) is enhanced with increasing the thickness of GaN cap layer. In addition, compared with the electroluminescence measurement results, we focus on the difference of localization states and defects in three samples induced by various cap thickness to explain the anomalies in room temperature photoluminescence measurements. We found that too thin GaN cap layer will exacerbates the inhomogeneity of localization states in InGaN QW layer, and too thick GaN cap layer will generate more defects in GaN cap layer.

scholarly journals The frontiers of functionalized graphene-based nanocomposites as chemical sensors

2021 ◽  
Vol 10 (1) ◽  
pp. 330-369
Author(s):  
Norizan M. Nurazzi ◽  
Norli Abdullah ◽  
Siti Z. N. Demon ◽  
Norhana A. Halim ◽  
Ahmad F. M. Azmi ◽  
...  
Keyword(s):  
Electron Mobility ◽  
Room Temperature ◽  
Chemical Sensor ◽  
Performance Enhancement ◽  
Ballistic Transport ◽  
Quantum Hall ◽  
Single Atom ◽  
Research Progress ◽  
Thick Sheet ◽  
High Electron

Abstract Graphene is a single-atom-thick sheet of sp2 hybridized carbon atoms that are packed in a hexagonal honeycomb crystalline structure. This promising structure has endowed graphene with advantages in electrical, thermal, and mechanical properties such as room-temperature quantum Hall effect, long-range ballistic transport with around 10 times higher electron mobility than in Si and thermal conductivity in the order of 5,000 W/mK, and high electron mobility at room temperature (250,000 cm2/V s). Another promising characteristic of graphene is large surface area (2,630 m2/g) which has emerged so far with its utilization as novel electronic devices especially for ultrasensitive chemical sensor and reinforcement for the structural component applications. The application of graphene is challenged by concerns of synthesis techniques, and the modifications involved to improve the usability of graphene have attracted extensive attention. Therefore, in this review, the research progress conducted in the previous decades with graphene and its derivatives for chemical detection and the novelty in performance enhancement of the chemical sensor towards the specific gases and their mechanism have been reviewed. The challenges faced by the current graphene-based sensors along with some of the probable solutions and their future improvements are also being included.

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