GaInNAs Quantum Research Articles

GaInNas/GaAs QW Based Structures to Compensate Parasitic Effect of Quantum-Confined Stark Effect in Photodetector Applications

The inhomogeneities of multicomponent semiconductor alloys, as well as phase segregation, can be utilized for enhancement of photodetector absorption properties and thus its efficiency. In this paper, the influence of external electric field on the probability of light absorption in the GaInNAs quantum well is discussed. Both phenomenon: indium and nitrogen composition gradient as well as step-like quantum well are applied to design the QW with compensation of the Quantum-Confined Stark Effect (QCSE) Parasitic effect of QCSE results from decrease of the wave functions overlapping in the QWs placed in reverse biased junction, which finally decrease the efficiency of the photodetector.

Inhomogeneous GaInNAs quantum wells: their properties and utilization for improving of p-i-n and p-n junction photodetectors

Abstract A theoretical study of electronic structures and optical properties of GaInNAs/GaAs quantum wells has been performed. The inhomogeneous distributions of indium and nitrogen atoms along the growth direction were discussed as the main factors having significant impact on the QWs absorption efficiency. The study was performed by applying the band anticrossing model combined with the envelope function formalism and based on the material parameters which can be found in the literature. Indeed, the electronic band structure of 15 nm thick uniform Ga0.7In0.3N0.02As0.98/GaAs QW was computed together with electronic structures of several types of inhomogeneous QWs, with the same total content of In and N atoms. It was found that presented inhomogeneities lead to significant quantum wells potential modifications and thus to spatial separation of the electrons and holes wave functions. On the other hand, these changes have a significant impact on the absorption coefficient behavior. This influence has been studied on the basis of simulated photoreflectance spectra, which probe the absorption transitions between QW energy subbands. The electronic structure of inhomogeneous QWs under the influence of electric field has also been studied. Two different senses of electric field vector (of p-i-n and n-i-p junctions) have been considered and thus, the improvement of such types of QWs-photodetectors based on inhomogeneous GaInNAs QWs has been proposed.

English

III-V semiconductors components such as Gallium Arsenic (GaAs), Indium Antimony (InSb), Aluminum Arsenic (AlAs) and Indium Arsenic (InAs) have high carrier mobilities and direct energy gaps. This is making them indispensable for today’s optoelectronic devices such as semiconductor lasers and optical amplifiers at 1.3 μm wavelength operation. In fact, these elements are led to the invention of the Gallium Indium Nitride Arsenic (GaInNAs), where the lattice is matched to GaAs for such applications. This article is aimed to design dilute nitride GaInNAs quantum wells (QWs) enclosed between top and bottom of Aluminum (Gallium) Arsenic Al(Ga)As distributed bragg mirrors (DBRs) using MATLAB® program. Vertical cavity semiconductor optical amplifiers (VCSOAs) structures are based on Fabry Perot (FP) method to design optical gain and bandwidth gain to be operated in reflection and transmission modes. The optical model gives access to the contact layer of epitaxial structure and the reflectivity for successive radiative modes, their lasing thresholds, emission wavelengths and optical field distributions in the laser cavity.

Determination of composition of non-homogeneous GaInNAs layers

Dilute nitride GaInNAs alloys grown on GaAs have become perspective materials for so called low-cost GaAs-based devices working within the optical wavelength range up to 1.6μm. The multilayer structures of GaInNAs/GaAs multi-quantum well (MQW) samples usually are analyzed by using high resolution X-ray diffraction (HRXRD) measurements. However, demands for precise structural characterization of the GaInNAs containing heterostructures requires taking into consideration all inhomogeneities of such structures. This paper describes some of the material challenges and progress in structural characterization of GaInNAs layers. A new algorithm for structural characterization of dilute nitrides which bounds contactless electro-reflectance (CER) or photo-reflectance (PR) measurements and HRXRD analysis results together with GaInNAs quantum well band diagram calculation is presented. The triple quantum well (3QW) GaInNAs/GaAs structures grown by atmospheric-pressure metalorganic vapor-phase epitaxy (AP-MOVPE) were investigated according to the proposed algorithm. Thanks to presented algorithm, more precise structural data including the nonuniformity in the growth direction of GaInNAs/GaAs QWs were achieved. Therefore, the proposed algorithm is mentioned as a nondestructive method for characterization of multicomponent inhomogeneous semiconductor structures with quantum wells.

615 nm GaInNAs VECSEL with output power above 10 W.

A high-power optically-pumped vertical-external-cavity surface-emitting laser (VECSEL) generating 10.5 W of cw output power at 615 nm is reported. The gain mirror incorporated 10 GaInNAs quantum wells and was designed to have an emission peak in the 1230 nm range. The fundamental emission was frequency doubled to the red spectral range by using an intra-cavity nonlinear LBO crystal. The maximum optical-to-optical conversion efficiency was 17.5%. The VECSEL was also operated in pulsed mode by directly modulating the pump laser to produce light pulses with duration of ~1.5 µs. The maximum peak power for pulsed operation (pump limited) was 13.8 W. This corresponded to an optical-to-optical conversion efficiency of 20.4%.

Optical properties and thermionic emission in solar cells with InAs quantum dots embedded within GaNAs and GaInNAs

The optical properties of p-i-n solar cells comprised of InAs quantum dots embedded within GaNAs and GaInNAs quantum wells are reported. Strain compensating and mediating GaNAs and GaInNAs layers shift the photoluminescence emission as well as absorption edge of the quantum dots to longer wavelengths. GaNAs and GaInNAs quantum wells contribute also to extending the absorption edge. In addition, the use of GaNAs and GaInNAs layers enhances the thermal escape of electrons from QDs by introducing steps for electrons to the GaAs conduction band.

Improved luminescence from tensile-strained compound semiconductor quantum wells with dielectric-rod photonic crystals

We investigated the use of dielectric-rod photonic crystals on a tensile-strained dilute nitride gain medium. After applying the patterned photonic crystal rods to GaInNAs quantum wells with a heterostructure having optical confinement, we observed enhanced extracted luminescence efficiency from the surface depending on the correlated variation in the transverse magnetic photonic band structure.

Instability of structural defects generated by electron irradiation in GaInNAs quantum wells

Electron irradiation is found to cause a large blue shift of photoluminescence from a 1.3-μm laser-like strain-compensated GaInNAs/GaNAs/GaAs quantum well structure when annealed after irradiation. The line shift is assigned to the presence of complex defect centers in the quantum wells. The defects are very unstable. The peak position and line shape of the spectra are restored to their original values by an ageing effect, which occurs even at room temperature. The mechanism causing the blue shift/red shift of photoluminescence is qualitatively described.

Effect of Small Microfabrication Damage on Optical Characteristics of Laser Structure with GaInNAs Quantum Well

We investigate the effect of micro-fabrication process damage on the photoluminescence characteristics of laser structures containing a GaInNAs and GaInAs quantum wells. By varying the size of the fabricated island structure, its impact on the photoluminescence intensity is studied. The GaInAs sample shows a strong decrease in its intensity with the reduction of the island size. In contrast, a slight increase is observed from the GaInNAs sample. This indicates the negligible impact of surface recombination on the GaInNAs sample, as well as the optical confinement within the micrometer-size island structure. The results suggest the feasibility of a GaInNAs gain medium for application to microfabricated optical devices.

Enhancement of activation energies of sharp photoluminescence lines for GaInNAs quantum wells due to quantum confinement

It is shown that localized emission from GaInNAs quantum wells (QW) is composed of sharp photoluminescence (PL) lines. Spectral position of these PL lines varies in a very broad range (∼150 meV) but the activation energy of each line is the same within the experimental uncertainty and equals ∼11 meV. This value is higher than in bulk GaInNAs (∼6 meV) and corresponds very well to electron–hole attraction in GaInNAs QW. It means that the source of these sharp PL lines are excitons localized on deep centres, which can recombine radiatively while the thermal energy is smaller than the Coulomb attraction between electrons and holes. Because of this the localized emission composing of sharp PL lines is observed at low temperatures and quenched much faster for GaInNAs layers than GaInNAs/GaAs QWs.

Quantum Confinement Stark Effect of Different Gainnas Quantum Well Structures

The quantum confinement Stark effect of three types of GaInNAs quantum wells, namely single square quantum well, stepped quantum wells and coupled quantum wells, is investigated using the band anti-crossing model. The comparison between experimental observation and modeling result validate the modeling process. The effects of the external electric field and localized N states on the quantized energy shifts of these three structures are compared and analyzed. The external electric field applied to the QW not only changes the potential profile but also modulates the localized N states, which causes band gap energy shifts and increase of electron effective mass.

Modelling escape and capture processes in GaInNAs quantum well solar cells

AbstractCarrier escape and capture processes in a GaInA/GaAs quantum well (QW) and a GaInNAs/GaAs QW are compared through modelling using a rate equation approach. QW compositions corresponding to bandgaps of 0.983 eV, 1.000 eV and 1.100 eV are considered for applications in solar cells. For GaInAs a standard alloy model is used, including strain effects, while for GaInNAs the Band Anticrossing (BAC) model is used. The roles of 1. the conduction band QW barrier height and 2. the corresponding effective mass in affecting the electron escape and capture in the QW are considered in detail. The contribution of photogenerated currents from the barrier and QW are considered. The effect of QW depth is found to be larger than changes in the electron effective mass. (© 2013 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Optimisation of optical properties of a long-wavelength GaInNAs quantum-well laser diode

We report optimisation of optical properties of a strained GaInNAs/GaAs quantum-well laser, by taking into account the many-body effect theory and the bowing parameter. The theoretical transition energies and the GaInNAs bowing parameter are fitted into the photoluminescence spectrum of the GaInNAs quantum well, obtained in the experiment. The theoretical results for the photoluminescence spectrum and laser characteristics (light, current and voltage) exhibits a high degree of agreement with the experimental results.

Monte Carlo Simulations of the Influence of Localization Centres on Carrier Dynamics in GaInNAs Quantum Wells

Monte Carlo Simulations of the Influence of Localization Centres on Carrier Dynamics in GaInNAs Quantum Wells

Optical properties of hybrid quantum dot/quantum well active region based on GaAs system

We experimentally investigate the optical properties of a novel hybrid material/structure consisting of a GaInNAs quantum well and stacked InAs/InGaAs quantum dot layers on GaAs substrate. We demonstrate that the strong quantum confined Stark effect within the quantum well can effectively control well-dot detuning when reverse bias voltage is applied. With a combination of low- and room-temperature time resolved luminescence spectra we infer device absorption recovery time under 30 ps. These properties could be utilized in high-speed optoelectronics devices, in particular electro-absorption modulated lasers and reconfigurable multisection devices, where the hybrid quantum dots – quantum well material system could offer easily and rapidly interchangeable function, i.e., emission gain or variable attenuation, of each section depending on the external bias.

Influence of non-radiative recombination on photoluminescence decay time in GaInNAs quantum wells with Ga- and In-rich environments of nitrogen atoms

The influence of non-radiative recombination on the photoluminescence decay time (τPL) has been studied for GaInNAs/GaAs quantum wells with Ga- and In-rich environments of N atoms. At low temperatures, this influence is suppressed, due to the carrier localization phenomenon, which leads to a spectral dispersion of τPL. For investigated samples, this dispersion has been found to be in the range of ~0.2–2.0 ns. With the temperature increase, the free exciton emission starts to dominate instead of the localized exciton emission and the dispersion of τPL disappears. The dynamic of free exciton recombination is strongly influenced by the non-radiative recombination, which varies between samples, due to different concentration of non-radiative centers. The study of influence of non-radiative recombination on τPL has been performed at 180 K, since this temperature is high enough to eliminate the localized emission and activate non-radiative recombination and low enough to observe excitonic emission without strong contribution of free carrier recombination when the sample is excited with low power. It was observed that, for as-grown samples, the τPL increases from 0.14 to 0.25 ns with the change in As/III beam equivalent pressure ratio from 3.8 to 12.1 (in this case, it corresponds to the change in nitrogen nearest-neighbor environment from Ga- to In-rich), whereas, after annealing (i.e., also the change from Ga-rich to In-rich environment of N atoms), this time increases 2–4 times, depending on the As/III ratio. It has been concluded that the τPL is influenced by point defects rather than the nitrogen nearest-neighbor environment, but their concentration is correlated with the type of nitrogen environment.

Long-wavelength MBE grown GaInNAs quantum well laser emitting at 1270 nm

In this paper, we report on comprehensive theoretical optical properties analysis and experimental device electrical-optical characterization of long wavelength GaInNAs edge-emitting laser diode. The theoretical analysis demonstrates that a high quality GaInNAs active region and device design are devised, where high material gain near 1.3 μm and optimal optical mode confinement are calculated. Experimentally, room temperature lasing emission around 1.27 μm with threshold current densities of 670–810 A/cm2 is obtained from the fabricated broad area GaInNAs edge-emitting laser grown by molecular beam epitaxy technique.

7.4 W yellow GaInNAs-based semiconductor disk laser

A high power frequency-doubled semiconductor disk laser emitting 7.4 W of output power at the yellow wavelength range is reported. Fundamental emission at around 1190 nm was achieved using a high quality gain mirror incorporating GaInNAs quantum wells. The infrared radiation was frequency doubled using an intracavity beta barium borate crystal. To the best of the authors knowledge, this is the highest output power reported for a single-chip semiconductor disk laser emitting yellow radiation.

Determination of Exciton Binding Energy of GaInNAs Quantum Well Structures by Piezoelectric Photothermal Spectroscopy Compared with Photoreflectance Measurements

Determination of Exciton Binding Energy of GaInNAs Quantum Well Structures by Piezoelectric Photothermal Spectroscopy Compared with Photoreflectance Measurements

Determination of Exciton Binding Energy of GaInNAs Quantum Well Structures by Piezoelectric Photothermal Spectroscopy Compared with Photoreflectance Measurements

The exciton binding energies (Exb) of a dilute nitride Ga1-yInyN0.012As0.988 layer (y = 0.0 to 4.5%) with the thickness of 100 nm were determined by both piezoelectric photothermal (PPT) and photoreflectance (PR) spectroscopies. Curve-fitting analyses were carried out using a three-dimensional direct allowed-transition model with the Voigt function as a convolution integral for PPT and with Aspnes' formula for PR. The observed estimation error for PR was about two times larger than that of PPT. Therefore, we conclude that PPT is a novel methodology for determining Exb when it is small and two expected critical energies exist in the narrow energy region.