Influence of template properties and quantum well number on stimulated emission from Al0.7Ga0.3N/Al0.8Ga0.2N quantum wells

ABSTRACTEdge emission characteristics of optically pumped GaN-AlGaN double heterostructures and quantum wells are examined. The samples, which were grown by metalorganic vapor phase epitaxy, are photoexcited with light from a pulsed nitrogen laser. The pump light is focused to a narrow stripe on the sample surface, oriented perpendicular to a cleaved edge, and the edge luminescence is collected and analyzed. We first compare emission characteristics of highly excited GaN-AlGaN double heterostructures grown simultaneously on SiC and sapphire substrates. Polarization resolved spectral properties of edge luminescence from both structures is studied as a function of pump intensity and excitation stripe length. Characteristics indicative of stimulated emission are observed, particularly in the sample grown on SiC. We then present results demonstrating laser emission from a GaN-AlGaN separate-confinement quantum-well heterostructure. At high pump intensities, band edge emission from the quantum well exhibits five narrow (∼1 Å) modes which are evenly spaced by 10Å to within the resolution of the spectrometer. This represents the first demonstration of laser action in a GaN-based quantum-well structure.

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Stimulated Emission from Single- and Multiple-Quantum-Well GaN-AlGaN Separate-Confinement Heterostructures

MRS Proceedings ◽

10.1557/proc-449-1203 ◽

1996 ◽

Vol 449 ◽

Author(s):

D. A. S. Loeber ◽

N. G. Anderson ◽

J. M. Redwing ◽

J. S. Flynn ◽

G. M. Smith ◽

...

Keyword(s):

Quantum Well ◽

Quantum Wells ◽

Optical Pumping ◽

Multiple Quantum Well ◽

Emission Spectra ◽

Stimulated Emission ◽

Emission Characteristics ◽

Multiple Quantum ◽

Photoluminescence Properties ◽

Single Quantum Well

ABSTRACTStimulated emission characteristics are examined for GaN-AlGaN separate-confinement quantum-well heterostructures grown by MOVPE on 4H-SiC substrates. We specifically focus on comparison of structures with different quantum well active region designs. Polarization resolved edge emission spectra and stimulated emission thresholds are obtained under optical pumping using a stripe excitation geometry. Stimulated emission characteristics are studied as a function of the number of quantum wells in the structure, and are correlated with surface photoluminescence properties. We find reduced stimulated emission thresholds and increased surface photoluminescence intensities as the number of quantum wells is reduced, with the best results obtained for a single-quantum-well structure. These results should provide useful information for the design of GaN-based quantum well lasers.

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Optical Properties of Pseudomorphic InxGa1−xAs Quantum Wells

MRS Proceedings ◽

10.1557/proc-77-437 ◽

1986 ◽

Vol 77 ◽

Cited By ~ 5

Author(s):

N. G. Anderson ◽

Y. C. Lo ◽

R. M. Kolbas

Keyword(s):

Quantum Well ◽

Quantum Wells ◽

Excitation Intensity ◽

Stimulated Emission ◽

Luminescence Properties ◽

Photoluminescence Spectra ◽

Quantum Well Structures ◽

Single Feature ◽

Increasing Temperature ◽

Confining Layers

ABSTRACTThe luminescence properties of MBE-grown pseudomorphic InxGa1−xAs—GaAs quantum-well structures are examined as a function of photoexcitation intensity and temperature. The structures examined consist of single In0.28Ga0.72As or (isolated) multiple In0.16Ga0.84As pseudomorphic wells sandwiched between thick, unstrained GaAs confining layers. Low-temperature photoluminescence spectra for these samples, which range in quantum-well thickness from 17 Å to 50 Å, consist of a single feature attributable to transitions associated with n = 1 electron and j = 3/2, Mj = 3/2 > - hole states. Spectral widths of these peaks are very narrow (7–11 meV), even for a heavily spike-doped sample (Si, ND ∼ 1018 spike-doped at well center). Emission intensities for the quantum-well structures are studied as a function of excitation intensity over the range 3 × 102 ≤ Pex ≤ 6 x 1O4 W/cm2, and one of the samples (x = 0.16, 50 Å undoped wells) prepared as a laser structure is shown to support stimulated emission at an excitation intensity < 104 W/cm2. The excellent luminescence properties of these structures are shown to degrade rapidly with increasing temperature, with radiative efficiencies dropping more than two orders of magnitude over the temperature range 20K – 180K. One possible explanation for this behavior is proposed.

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The role of piezoelectric fields in GaN-based quantum wells

MRS Internet Journal of Nitride Semiconductor Research ◽

10.1557/s1092578300000879 ◽

1998 ◽

Vol 3 ◽

Cited By ~ 123

Author(s):

Andreas Hangleiter ◽

Jin Seo Im ◽

H. Kollmer ◽

S. Heppel ◽

J. Off ◽

...

Keyword(s):

Quantum Well ◽

Quantum Wells ◽

Spatial Separation ◽

Stimulated Emission ◽

Wurtzite Phase ◽

Single Quantum Well ◽

Quantum Well Structures ◽

Free Case ◽

Piezoelectric Field ◽

Piezoelectric Fields

In this contribution, we focus on the consequences of the piezoelectric field, which is an inherent consequence of the commonly used wurtzite phase of GaN, on the optical properties of strained GaN-based quantum well structures. We demonstrate that both in GaN/AlGaN and in GaInN/GaN single quantum well structures, the piezoelectric field leads to a Stark-shift of the fundamental optical transitions, which can lead to luminescence emission far below the bulk bandgap. Due to the spatial separation of the electron and hole wavefunctions in such structures, the oscillator strength of these transitions may become extremely small, many orders of magnitude lower than in the field-free case. From specially designed structures, we can even determine the sign of the piezoelectric field and relate it to the polarity of the layers. Under high-excitation conditions, as found in a laser diode, the piezoelectric field is almost completely screened by the injected carriers. As a consequence, the stimulated emission is significantly blue-shifted compared to the photoluminescence, which has sometimes been confused with localization effects.

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Characterization of GaAs/AlGaAs quantum wells and quantum wires by chemical lattice imaging

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100171419 ◽

1994 ◽

Vol 52 ◽

pp. 736-737

Author(s):

A. Carlsson ◽

J.-O. Malm ◽

A. Gustafsson

Keyword(s):

Quantum Well ◽

Quantum Wells ◽

Quantum Wires ◽

Vapour Phase ◽

Quantitative Information ◽

Lattice Imaging ◽

Vapour Phase Epitaxy ◽

Metalorganic Vapour Phase Epitaxy ◽

High Resolution Images

In this study a quantum well/quantum wire (QW/QWR) structure grown on a grating of V-grooves has been characterized by a technique related to chemical lattice imaging. This technique makes it possible to extract quantitative information from high resolution images.The QW/QWR structure was grown on a GaAs substrate patterned with a grating of V-grooves. The growth rate was approximately three monolayers per second without growth interruption at the interfaces. On this substrate a barrier of nominally Al0.35 Ga0.65 As was deposited to a thickness of approximately 300 nm using metalorganic vapour phase epitaxy . On top of the Al0.35Ga0.65As barrier a 3.5 nm GaAs quantum well was deposited and to conclude the structure an additional approximate 300 nm Al0.35Ga0.65 As was deposited. The GaAs QW deposited in this manner turns out to be significantly thicker at the bottom of the grooves giving a QWR running along the grooves. During the growth of the barriers an approximately 30 nm wide Ga-rich region is formed at the bottom of the grooves giving a Ga-rich stripe extending from the bottom of each groove to the surface.

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Characterisation of multilayer materials using a position-sensitive atom probe

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100176253 ◽

1990 ◽

Vol 48 (4) ◽

pp. 624-625

Author(s):

RAD Mackenzie ◽

G D W Smith ◽

A. Cerezo ◽

J A Liddle ◽

CRM Grovenor ◽

...

Keyword(s):

Quantum Well ◽

Quantum Wells ◽

Spatial Information ◽

Chemical Vapour ◽

Atom Probe ◽

Organic Chemical ◽

Growth Stages ◽

Multiple Quantum ◽

Quartz Wool ◽

Position Sensitive

The position sensitive atom probe (POSAP), described briefly elsewhere in these proceedings, permits both chemical and spatial information in three dimensions to be recorded from a small volume of material. This technique is particularly applicable to situations where there are fine scale variations in composition present in the material under investigation. We report the application of the POSAP to the characterisation of semiconductor multiple quantum wells and metallic multilayers.The application of devices prepared from quantum well materials depends on the ability to accurately control both the quantum well composition and the quality of the interfaces between the well and barrier layers. A series of metal organic chemical vapour deposition (MOCVD) grown GaInAs-InP quantum wells were examined after being prepared under three different growth conditions. These samples were observed using the POSAP in order to study both the composition of the wells and the interface morphology. The first set of wells examined were prepared in a conventional reactor to which a quartz wool baffle had been added to promote gas intermixing. The effect of this was to hold a volume of gas within the chamber between growth stages, leading to a structure where the wells had a composition of GalnAsP lattice matched to the InP barriers, and where the interfaces were very indistinct. A POSAP image showing a well in this sample is shown in figure 1. The second set of wells were grown in the same reactor but with the quartz wool baffle removed. This set of wells were much better defined, as can be seen in figure 2, and the wells were much closer to the intended composition, but still with measurable levels of phosphorus. The final set of wells examined were prepared in a reactor where the design had the effect of minimizing the recirculating volume of gas. In this case there was again further improvement in the well quality. It also appears that the left hand side of the well in figure 2 is more abrupt than the right hand side, indicating that the switchover at this interface from barrier to well growth is more abrupt than the switchover at the other interface.

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Asymmetric Ge/SiGe coupled quantum well modulators

Nanophotonics ◽

10.1515/nanoph-2021-0007 ◽

2021 ◽

Vol 10 (6) ◽

pp. 1765-1773

Author(s):

Yi Zhang ◽

Jianfeng Gao ◽

Senbiao Qin ◽

Ming Cheng ◽

Kang Wang ◽

...

Keyword(s):

Energy Consumption ◽

Quantum Well ◽

Quantum Wells ◽

High Speed ◽

Low Voltage ◽

Extinction Ratio ◽

High Frequency Response ◽

Modulation Format ◽

Silicon Photonic ◽

Coupled Quantum Well

Abstract We design and demonstrate an asymmetric Ge/SiGe coupled quantum well (CQW) waveguide modulator for both intensity and phase modulation with a low bias voltage in silicon photonic integration. The asymmetric CQWs consisting of two quantum wells with different widths are employed as the active region to enhance the electro-optical characteristics of the device by controlling the coupling of the wave functions. The fabricated device can realize 5 dB extinction ratio at 1446 nm and 1.4 × 10−3 electrorefractive index variation at 1530 nm with the associated modulation efficiency V π L π of 0.055 V cm under 1 V reverse bias. The 3 dB bandwidth for high frequency response is 27 GHz under 1 V bias and the energy consumption per bit is less than 100 fJ/bit. The proposed device offers a pathway towards a low voltage, low energy consumption, high speed and compact modulator for silicon photonic integrated devices, as well as opens possibilities for achieving advanced modulation format in a more compact and simple frame.

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Thermoelectric Power in Quantum Confined Bismuth Under Classically Large Magnetic Field

MRS Proceedings ◽

10.1557/proc-216-465 ◽

1990 ◽

Vol 216 ◽

Cited By ~ 6

Author(s):

Kamakhya P. Ghatak ◽

S. N. Biswas

Keyword(s):

Magnetic Field ◽

Quantum Dots ◽

Quantum Well ◽

Film Thickness ◽

Quantum Wells ◽

Thermoelectric Power ◽

Large Magnetic Field ◽

Quantum Well Wires ◽

Electron Dispersion ◽

Theoretical Results

ABSTRACTIn this paper we studied the thermoelectric power under classically large magnetic field (TPM) in quantum wells (QWs), quantum well wires (QWWS) and quantum dots (QDs) of Bi by formulating the respective electron dispersion laws. The TPM increases with increasing film thickness in an oscillatory manner in all the cases. The TPM in QD is greatest and the least for quantum wells respectively. The theoretical results are in agreement with the experimental observations as reported elsewhere.

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LINEAR AND NONLINEAR INTERSUBBAND OPTICAL ABSORPTION OF FINITE AND INFINITE SEMI-PARABOLIC QUANTUM WELLS

Modern Physics Letters B ◽

10.1142/s0217984911025882 ◽

2011 ◽

Vol 25 (07) ◽

pp. 497-507 ◽

Cited By ~ 1

Author(s):

M. J. KARIMI ◽

A. KESHAVARZ ◽

A. POOSTFORUSH

Keyword(s):

Refractive Index ◽

Optical Properties ◽

Optical Absorption ◽

Quantum Well ◽

Quantum Wells ◽

Resonant Peak ◽

Energy Eigenvalues ◽

Finite Case ◽

Infinite Case ◽

Index Changes

In this work, the optical absorption coefficients and the refractive index changes for the infinite and finite semi-parabolic quantum well are calculated. Numerical calculations are performed for typical GaAs / Al x Ga 1-x As semi-parabolic quantum well. The energy eigenvalues and eigenfunctions of these systems are calculated numerically. Optical properties are obtained using the compact density matrix approach. Results show that the energy eigenvalues and the matrix elements of the infinite and finite cases are different. The calculations reveal that the resonant peaks of the optical properties of the finite case occur at lower values of the incident photon energy with respect to the infinite case. Results indicate that the maximum value of the refractive index changes for the finite case are greater than that of the infinite case. Our calculations also show that in contrast to the infinite case, the resonant peak value of the total absorption coefficient in the case of the finite well is a non-monotonic function of the semi-parabolic confinement frequency.

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