scholarly journals Исследование напряжeнности внутренних электрических полей в активной области светодиодных структур на основе InGaN/GaN с разным числом квантовых ям методом спектроскопии электропропускания

2020 ◽  
Vol 54 (4) ◽  
pp. 420
Author(s):  
А.Э. Асланян ◽  
Л.П. Авакянц ◽  
А.В. Червяков ◽  
А.Н. Туркин ◽  
С.С. Мирзаи ◽  
...  
Keyword(s):  
Active Region ◽  
Quantum Well ◽  
Quantum Wells ◽  
Electric Fields ◽  
Green Emission ◽  
Spectral Lines ◽  
Interband Transitions ◽  
Barrier Type ◽  
Piezoelectric Field

Abstract The internal electric fields of InGaN/GaN-based green-emission LED heterostructures with various numbers of quantum wells in the active region are investigated by electrotransmission spectroscopy. The frequencies of the observed spectral lines are attributed to possible types of interband transitions. An increase in the number of interband transitions of the “quantum well—quantum barrier” type with an increase in the number of quantum wells is found. This is explained by the nonidentical degree of segregation of In atoms in different GaN barriers layers. The strength of internal electric fields in quantum wells is calculated for various values of the bias of the p – n junction using a series of electrotransmission spectra. It is found that the strength of the internal piezoelectric field decreases from 3.20 to 2.82 MV/cm with an increase in the number of quantum wells.

scholarly journals Stacked Dual-Band Quantum Well Infrared Photodetector Based on Double-Layer Gold Disk Enhanced Local Light Field

Nanomaterials ◽  
2021 ◽  
Vol 11 (10) ◽  
pp. 2695
Author(s):  
Chang Liu ◽  
Xuan Zuo ◽  
Shaohui Xu ◽  
Lianwei Wang ◽  
Dayuan Xiong
Keyword(s):  
Active Region ◽  
Quantum Well ◽  
Quantum Wells ◽  
Double Layer ◽  
Enhancement Factor ◽  
Coupling Efficiency ◽  
Dual Band ◽  
Enhancement Effect ◽  
Infrared Photodetector ◽  
Quantum Well Infrared Photodetector

We propose a stacked dual-band quantum well infrared photodetector (QWIP) integrated with a double-layer gold disk. Two 10-period quantum wells (QW) operating at different wavelengths are stacked together, and gold nano-disks are integrated on their respective surfaces. Numerical calculations by finite difference time domain (FDTD) showed that the best enhancement can be achieved at 13.2 and 11.0 µm. By integrating two metal disks, two plasmon microcavity structures can be formed with the substrate to excite localized surface plasmons (LSP) so that the vertically incident infrared light can be converted into electric field components perpendicular to the growth direction of the quantum well (EZ). The EZ electric field component can be enhanced up to 20 times compared to the incident light, and it is four times that of the traditional two-dimensional hole array (2DHA) grating. We calculated the enhancement factor and coupling efficiency of the device in the active region of the quantum well. The enhancement factor of the active region of the quantum well on the top layer remains above 25 at the wavelength of 13.2 μm, and the enhancement factor can reach a maximum of 45. Under this condition, the coupling efficiency of the device reaches 2800%. At the wavelength of 11.0 μm, the enhancement factor of the active region of the quantum well at the bottom is maintained above 6, and the maximum can reach about 16, and the coupling efficiency of the device reaches 800%. We also optimized the structural parameters and explored the influence of structural changes on the coupling efficiency. When the radius (r1, r2) of the two metal disks increases, the maximum coupling efficiency will be red-shifted as the wavelength increases. The double-layer gold disk structure we designed greatly enhances the infrared coupling of the two quantum well layers working at different wavelengths in the dual-band quantum well infrared photodetector. The structure we designed can be used in stacked dual-band quantum well infrared photodetectors, and the active regions of quantum wells working at two wavelengths can enhance the photoelectric coupling, and the enhancement effect is significant. Compared with the traditional optical coupling structure, the structure we proposed is simpler in process and has a more significant enhancement effect, which can meet the requirements of working in complex environments such as firefighting, night vision, and medical treatment.

scholarly journals Photo- and cathodoluminescence investigations of piezoelectric GaN/AlGaN quantum wells

2000 ◽  
Vol 639 ◽  
Author(s):  
E.M. Goldys ◽  
M. Godlewski ◽  
M.R. Phillips ◽  
A.A. Toropov
Keyword(s):  
Quantum Well ◽  
Quantum Wells ◽  
Electric Fields ◽  
Free Exciton ◽  
Multiple Quantum Well ◽  
Depth Profiling ◽  
Multiple Quantum ◽  
Recombination Mechanism ◽  
Decay Times ◽  
Piezoelectric Fields

ABSTRACTWe have examined multiple quantum well AlGaN/GaN structures with several quantum wells of varying widths. The structures had strain-free quantum wells and strained barriers. Strong piezoelectric fields in these structures led to a large red shift of the PL emission energies and long decay times were also observed. While the peak energies could be modelled using the effective mass approximation, the calculated free exciton radiative lifetimes were much shorter than those observed in experiments, indicating an alternative recombination mechanism, tentatively attributed to localised excitons. Cathodoluminescence depth profiling revealed an unusually small penetration range of electrons suggesting that electron-hole pairs preferentially remain within the multiple quantum well region due to the existing electric fields. Spatial fluctuations of the cathodoluminescence intensity were also observed.

TERAHERTZ EMISSION FROM ELECTRICALLY PUMPED SILICON GERMANIUM INTERSUBBAND DEVICES

2007 ◽  
Vol 17 (01) ◽  
pp. 115-120
Author(s):  
N. Sustersic ◽  
S. Kim ◽  
P.-C. Lv ◽  
M. Coppinger ◽  
T. Troeger ◽  
...  
Keyword(s):  
Quantum Well ◽  
Quantum Wells ◽  
Silicon Germanium ◽  
Heavy Hole ◽  
Light Hole ◽  
Spectral Lines ◽  
Intersubband Transitions ◽  
Terahertz Emission ◽  
Drive Current ◽  
Quantum Well Width

In this paper, we report on current pumped THz emitting devices based on intersubband transitions in SiGe quantum wells. The spectral lines occurred in a range from 5 to 12 THz depending on the quantum well width, Ge concentration in the well, and device temperature. A time-averaged power of 15 nW was extracted from a 16 period SiGe/Si superlattice with quantum wells 22 Å thick, at a device temperature of 30 K and a drive current of 550 mA. A net quantum efficiency of approximately 3 × 10-4 was calculated from the power and drive current, 30 times higher than reported for comparable quantum cascades utilizing heavy-hole to heavy-hole transitions and, taking into account the number of quantum well periods, approximately four times larger than for electroluminescence reported previously from a device utilizing light-hole to heavy-hole transitions.

Effect of Electric Fields in Coupled Double Quantum Wells

1987 ◽  
Vol 102 ◽  
Author(s):  
Y. J. Chen ◽  
Emil S. Koteles ◽  
B. Elman ◽  
C. A. Armiento
Keyword(s):  
Quantum Well ◽  
Quantum Wells ◽  
Electric Fields ◽  
Stark Effect ◽  
Double Quantum ◽  
Single Quantum Well ◽  
Quantum Confined Stark Effect ◽  
Quantum Well Structure ◽  
Double Quantum Well ◽  
Novel Structure

ABSTRACTWe present a detailed experimental study of the influence of electric fields on exciton states in a GaAs/AlGaAs coupled double quantum well structure and discuss the advantages of using this novel structure. The coupling of electronic states in the two quantum wells, due to the narrowness of the barrier between them, leads to an enhancement of the quantum-confined Stark effect (by as much as five times that of the single quantum well case). From the measured energies of the exciton transitions, splittings of the levels in a coupled double quantum well structure were derived without recourse to a theoretical model.

SHALLOW DONORS IN A COUPLED TRIPLE GRADED QUANTUM WELL UNDER THE ELECTRIC AND MAGNETIC FIELDS

2006 ◽  
Vol 13 (04) ◽  
pp. 397-401 ◽  
Author(s):  
E. KASAPOGLU ◽  
H. SARI ◽  
I. SÖKMEN
Keyword(s):  
Binding Energy ◽  
Quantum Well ◽  
Quantum Wells ◽  
Electric Fields ◽  
Growth Direction ◽  
Physical Parameters ◽  
Donor Impurity ◽  
Quantum Well Structures ◽  
Hydrogenic Donor Impurity ◽  
Electric And Magnetic Fields

The binding energy of the donor in three different shaped triple graded GaAs -( Ga , Al ) As quantum wells which is obtained by changing the depth of the central-well potential (Vo) is calculated by using a variational approach. The results have been obtained in the presence of uniform magnetic and electric fields applied along the growth direction as a function of the impurity position. In addition, we also give the binding energy of the hydrogenic donor impurity for triple square quantum wells having the same physical parameters with triple graded quantum well structures in order to see the effect of different geometric confinements on the donor impurity binding energy.

High-Resolution Spectroscopy of Individual Quantum Dots in Wells

MRS Bulletin ◽  
1998 ◽  
Vol 23 (2) ◽  
pp. 44-48 ◽  
Author(s):  
Daniel Gammon
Keyword(s):  
Quantum Well ◽  
Quantum Wells ◽  
Inhomogeneous Broadening ◽  
Spectral Lines ◽  
Laser Spot ◽  
High Resolution Spectroscopy ◽  
Semiconductor Quantum Dot ◽  
Interface Fluctuations ◽  
Series Of Experiments ◽  
Nanostructure Systems

Currently spectroscopists are studying many semiconductor quantum-dot (QD) systems in great detail because of their scientific and technological importance. However as in all nanostructure systems in which significant confinement energies exist, size fluctuations lead to inhomogeneous broadening of the spectral lines. This blurring of the spectra severely reduces the amount of information obtainable from spectroscopy. The finding has initiated an effort to isolate optically and study spectroscopically individual QDs. Studies involving individual QDs in most QD systems have been published. Here the results of a series of experiments are reviewed on GaAs QDs defined by interface fluctuations in narrow GaAs quantum wells. These experiments demonstrate the elegance and potential of single-QD spectroscopy.An example of single-QD photoluminescence (PL) spectroscopy appears in Figure 1. The spectra shown were obtained at a temperature of 6 K by successively reducing the size of the laser spot on a GaAs quantum-well sample through the use of small apertures in a metal mask. The bottom trace is a PL spectrum obtained with a macroscopic laser spot diameter of 25μm. The spectrum shows two broad peaks corresponding to the recombination of excitons in parts of the quantum well that are either 10 or 11 monolayers wide (2.8 or 3.1 nm). The spectrum is strongly inhomogeneously broadened as shown most directly by a reduction in the aperture size. The relatively broad lines break up into a decreasing number of extraordinarily narrow PL spikes as the aperture is reduced to submicroscopic dimensions. These PL spikes arise from excitons localized in individual QD potentials. Remarkably the linewidth decreases from several meV in the ensemble-averaged spectrum (25-μm aperture) to 10s of μeV in the single QD spectra, corresponding to an effective improvement in resolution of two orders in magnitude. By probing individual QDs, it becomes possible to resolve directly a number of phenomena that previously were hidden in the inhomogeneous linewidth.

scholarly journals Photoluminescence measurements on GaN/AlGaN modulation doped quantum wells

1999 ◽  
Vol 4 (1) ◽  
Author(s):  
J. Dalfors ◽  
J. P. Bergman ◽  
P.O. Holtz ◽  
B. Monemar ◽  
H. Amano ◽  
...  
Keyword(s):  
Quantum Well ◽  
Quantum Wells ◽  
Electron Gas ◽  
Energy Transition ◽  
Photoluminescence Spectra ◽  
Photoluminescence Decay ◽  
Fermi Edge ◽  
Decay Times ◽  
Piezoelectric Field ◽  
Good Agreement

Photoluminescence spectra were measured for 100 Å wurtzite GaN AlGaN modulation doped quantum wells. Three well-resolved peaks originate from the quantum well. The theoretically calculated confinement energies have been compared to the experimental energy positions and found to be in good agreement with the data, assuming that the piezoelectric field is largely screened by the electron gas. The highest energy transition may originate from the Fermi edge, consistent with the temperature dependence of the photoluminescence. Decay times for the different transitions indicate that the photoexcited holes are localized.

Sign of the Piezoelectric Field in Asymmetric GaInN/AlGaN/GaN Single and Double Quantum Wells on SiC

1999 ◽  
Vol 595 ◽  
Author(s):  
Jin Seo Im ◽  
A. Hangleiter ◽  
J. Off ◽  
F. Scholz
Keyword(s):  
Quantum Well ◽  
Quantum Wells ◽  
Oscillator Strength ◽  
Double Quantum ◽  
Barrier Structure ◽  
Time Resolved ◽  
Double Quantum Well ◽  
First Case ◽  
Algan Barrier ◽  
Piezoelectric Field

AbstractWe study both GaInN/GaN/AlGaN quantum wells with an asymmetric barrier structure grown on SiC substrate and GaN/AlGaN asymmetric double quantum well (ADQW) structures. In the first case, a time-resolved study reveals an enhanced oscillator strength when the AlGaN barrier is on top of the GaInN quantum well. In comparison to our previous study of the same structure grown on sapphire, we find that the sign of the field is the same in both cases: the field points towards the substrate. In the case of ADQW, we observed not only intrawell transitions of both a 4 nm and a 2 nm QW separated by a 2.5 nm AlGaN barrier but also an interwell transition between the two QWs in the photoluminescence. The lifetimes and emission energies of the transitions can be well explained by the existence of the piezoelectric field built in the QWs.

Profiling electric fields in GaN/InGaN/GaN single quantum wells by electron holography

2000 ◽  
Vol 639 ◽  
Author(s):  
Juan Cai ◽  
M. R. Mccartney ◽  
F. A. Ponce
Keyword(s):  
Quantum Well ◽  
Quantum Wells ◽  
Electric Fields ◽  
Potential Drop ◽  
Group Iii Nitrides ◽  
Electron Holography ◽  
Experimental Conditions ◽  
Quantum Well Structures ◽  
Indium Composition ◽  
Strained Quantum Well

ABSTRACTWe use electron holography to profile the local internal potential due to spontaneous polarization and piezoelectric effects in strained quantum well structures of wurtzitic group III nitrides. Profiles of the electrostatic potential across a GaN/InxGa1−xN/GaN quantum well structure show the existence of internal electric fields of about –2.2 ± 0.6 MV/cm, and a potential drop across the quantum well of 0.6 ± 0.16 V. The electric fields indicate an average indium composition of 15% in the quantum well, for a thickness of 2.7 nm. This indium composition compares well with measurements by energy-disperse spectroscopy of 18 ± 2 %. Screening effect is not observed under these experimental conditions.

THIRD-HARMONIC GENERATION OF WURTZITEGaN-BASED COUPLING QUANTUM WELLS WITH STRONG BUILT-IN ELECTRIC FIELDS

2007 ◽  
Vol 21 (27) ◽  
pp. 1837-1845 ◽  
Author(s):  
LI ZHANG
Keyword(s):  
Quantum Well ◽  
Density Matrix ◽  
Quantum Wells ◽  
Electric Fields ◽  
Harmonic Generation ◽  
Structural Parameters ◽  
Third Harmonic Generation ◽  
Matrix Approach ◽  
Third Harmonic ◽  
The Third

Based on the density matrix approach and iterative treatment, the third-harmonic generation (THG) susceptibility of a wurtzite nitride coupling quantum well (CQW) with strong built-in electric fields have been theoretically investigated. The band non-parabolicity effect of nitride heterostructures has been taken into account. A typical wurtzite AlGaN/GaN CQW are chosen to perform numerical calculations. The result shows that, the THG coefficients sensitively depend on the structural parameters of the CQW system. Moreover, a strong THG process can be realized in the nitride CQW by choosing a group of appropriate structural parameters and doped fraction.

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