InGaAsP Multiquantum Research Articles

Robust lasing of modes localized on marginally unstable periodic orbits

Many physical systems exhibit marginally unstable periodic orbits, which are nonhyperbolic families of periodic orbits appearing as segmented line structures with zero Lebesgue measure coexisting with hyperbolic components in phase space. Orbits in their vicinity escape in a subexponential manner which is in strong contrast to orbits near unstable periodic orbits which escape in an exponential way. By selectively exciting a series of modes in a rounded D-shape microdisk containing an InGaAsP multiquantum well, we experimentally demonstrate that marginally unstable periodic orbits can support a much more robust lasing than conventional unstable periodic orbits. Through numerical computations, we also compare quality factors of modes localized on marginally unstable periodic orbits and on stable periodic orbits.

Experimental evidence of hot carriers solar cell operation in multi-quantum wells heterostructures

We investigated a semiconductor heterostructure based on InGaAsP multi quantum wells (QWs) using optical characterizations and demonstrate its potential to work as a hot carrier cell absorber. By analyzing photoluminescence spectra, the quasi Fermi level splitting Δμ and the carrier temperature are quantitatively measured as a function of the excitation power. Moreover, both thermodynamics values are measured at the QWs and the barrier emission energy. High values of Δμ are found for both transition, and high carrier temperature values in the QWs. Remarkably, the quasi Fermi level splitting measured at the barrier energy exceeds the absorption threshold of the QWs. This indicates a working condition beyond the classical Shockley-Queisser limit.

Bonding InGaAsP/ITO/Si Hybrid Laser With ITO as Cathode and Light-Coupling Material

A 1.5-μ.m InGaAsP/ITO/Si hybrid laser with indium tin oxide (ITO) as both a cathode and a light-coupling material is presented. The InGaAsP gain structure with a transparent ITO cathode is flip-chip bonded onto a patterned silicon-on-insulator wafer. The light generated in the InGaAsP multiquantum wells is coupled through the ITO cathode into the Si waveguide to form an InGaAsP/ITO/Si hybrid laser. The threshold current density of this hybrid laser is 20 kA/cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> at 210 K. Due to the advantages of post-bonding and simplicity of the fabrication process, such a hybrid laser may be a promising Si light source.

A comparative study on ridge waveguide laser diodes with SiO2 and SiNx passivation layers

AbstractIn this study, we have reported the fabrication and device characteristics of metal organic chemical vapor deposition (MOCVD) grown 1.3‐µm InP‐based InGaAsP multiquantum well ridge waveguide laser diodes (LDs) for communication systems. The LD parameters such as threshold current, differential resistivity and output power for SiO2 and SiNx passivation layers have been compared. Fabricated LDs have a threshold current, differential resistivity and output power values of 42 mA, 20 Ω, 9.3 mW and 51 mA, 25 Ω, 6.8 mW for SiO2 and SiNx passivation layers, respectively. The analyses showed that the fabricated LD with SiO2 passivation layer has a better performance than the other one in the view of lower threshold current, differential resistivity and higher output power. Copyright © 2010 John Wiley &amp; Sons, Ltd.

Ga assisted in situ etching of AlGaInAs and InGaAsP multi quantum well structures using tertiarybutylchloride

In this work, we present studies on the in situ etching (ISE) technique using tertiarybutylchloride (TBCl) as etchant precursor in a metal organic vapour phase epitaxy (MOVPE) reactor. Experiments were made in PH 3 and PH 3-free environments at low pressures (50–100 mbar) and in a low-temperature regime (545–600 °C). In particular, the combination of standard reactive ion etching (RIE) and ISE for the realization of suitable mesa structures for device applications has been systematically investigated. In our etching experiments InP, InGaAsP and Al-containing multi quantum wells (MQWs) have been used as etching targets. Particular efforts were devoted to the etching of Al-containing structures. For this material, the addition of trimethylgallium (TMGa) during the etching resulted to be of key importance in providing good surface morphology and etching of the MQW structure. The role of Ga species in the etching mechanisms will be discussed. The dependence of surface morphology and mesa shape on etching conditions, in particular, temperature, chlorine concentration, gallium concentration and etching time, will be described.

Controlled intermixing in InGaAsP multiquantum wells by plasma immersion ion implantation of argon

In this paper, the diffusion enhanced intermixing effect in strained InGaAsP multiquantum wells due to plasma immersion ion implantation (PIII) of Ar + and post-implant annealing is presented. Firstly, we report that a 20 kV Ar + PIII at a fluency of 10 16 cm −2 together with a furnace anneal at 650°C resulted in an enhanced blue shift in the photoluminescence (PL) peak. It was also found that by varying the Ar + dose or the implantation energy, we could control the extent of the implantation induced intermixing. For a sample that had half of the surface shielded during implantation, a bandgap step was observed between the implanted and non-implanted regions. Our results indicate that one can use this technique for localised fine-tuning of the bandgap energy, thus demonstrating its potential as a processing step for the fabrication of integrated photonic devices.

Differential gain and threshold current of 1.3 μm tensile-strained InGaAsP multi quantum well buried-heterostructure lasers grown by metalorganic molecular beam epitaxial growth

The laser characteristics of 1.3 μm tensile-strained InGaAsP/InP multi quantum well (MQW) lasers were studied. The tensile strain of well layers ranged from 0.5% to 1.8%. The level of the strain dependence of the threshold current shows that the threshold current decreases drastically with increase in the tensile strain from 0.5% to 1.3%, while it stays almost constant in the 1.45%–1.8% range. Among all the samples, the 1.3% tensile-strained MQW laser shows superior performance in terms of minimum threshold current and maximum differential gain (∂g/∂N). The 1.3% tensile strain is the optimum level for the tensile-strained MQW buried-heterostructure lasers.

Be–Zn interdiffusion and its influence on InGaAsP lasers fabricated by hybrid growth of chemical beam epitaxy and metalorganic vapor phase epitaxy

We have studied the dopant redistribution between a chemical beam epitaxy (CBE) grown InGaAsP laser structure and a metalorganic vapor phase epitaxy overgrown InP layer. Secondary ion mass spectroscopy analysis reveals that Zn and Be atoms deeply interdiffuse in the adjacent InP layers for a Zn doping of 1018 cm−3 and that a fraction of Zn atoms go through the CBE InP and penetrate the laser structure guide layer. We have found that the Zn outdiffusion is significantly suppressed by reducing the Be doping concentration from 1018 to 5×1017 cm−3. As a result, for tensile-strained InGaAsP multiquantum well (MQW) buried-heterostructure (BH) lasers, the threshold current and internal loss decrease from 13 to 9 mA and 15 to 10 cm−1 by lowering the Be doping, respectively. InAsP MQW BH lasers have an internal loss of 5.5 cm−1.

Structural and optical properties of 1.3 μm wavelength tensile-strained InGaAsP multiquantum wells grown by metalorganic molecular beam epitaxy

Tensile strained 0.5%–1.8% InGaAsP multiquantum wells (MQWs) grown by metalorganic molecular beam epitaxy are comprehensively characterized by using transmission electron microscopy (TEM), x-ray, photoluminescence (PL), lifetime, photocurrent, and absorption measurements. Cross-sectional and plan-view TEM photos reveal that, irrespective of the strain values, the tensile strained well layers have flat surfaces in the growth direction and consist of fine parallelepipeds laterally. Optimizing the strain compensation conditions, i.e., keeping the net strain less than 0.3%, makes it possible to grow high optical quality MQWs with 1.8%-strained well layers. As the well strain increases from 0.5% to 1.45%, however, the PL intensities of the misfit-dislocation-free MQWs monotonically decrease and the minority carrier lifetime decreases from 1.4 to 0.9 nsec. The laser threshold current density decreased with increasing well strain in the 0.5%–1.3% range, decreased to 0.6 kA/cm2 at 1.3% and slightly increased in the 1.45%–1.8% range.

Microscopic photoluminescence characterization of 1.3-μm InAsP/InGaAsP strained multiquantum wells and laser diodes

This paper presents results of a microscopic photoluminescence (μ-PL) characterization of strained InAs0.5P0.5/InGaAsP multiquantum well (MQW) crystals with a series of well numbers (n=2–14). This method is useful in detecting misfit dislocations in the crystals, especially at the initial stage of their generation. The μ-PL intensity profile measurements of a laser diode (LD) cavity shows the intensity, being mainly influenced by the [01̄1]-directed misfit dislocations, is closely correlated to the threshold current of the LD.

Rate equation model of high-temperature performance of InGaAsP quantum well lasers

We present a steady-state phenomenological rate equation model describing the temperature dependence of the threshold current and slope efficiency of compressively strained InGaAsP multiquantum well lasers. The model is supported by measurements of differential carrier lifetime and gain carried out as a function of temperature. Differential gain, carrier density at transparency, and internal losses are shown to be the key parameters controlling the temperature sensitivity of our devices.

Effect of barrier recombination on the high temperature performance of quaternary multiquantum well lasers

We use spectrally resolved measurements of spontaneous emission to investigate the temperature characteristics of strained and lattice matched InGaAsP multiquantum well lasers. Carrier overflow into the barriers and separate confinement layers and the resulting recombination are demonstrated to be an important factor limiting high temperature performances in these devices. The barrier recombination does not saturate above threshold, instead it increases with the drive current. This effect is further enhanced with increased temperature. We show that the reduction in the barrier recombination correlates quantitatively with increased high temperature slope efficiency.

Metalorganic vapor phase epitaxy growth of InGaAsP multi quantum well laser diodes using entirely organic sources

Metalorganic vapor phase epitaxy (MOVPE) of InGaAsP multiple quantum well (MQW) lasers was performed by using entirely organic compounds as precursors. Tertiarybutylarsine (TBAs), tertiarybutylphosphine (TBP) and organic doping sources were used. The quality of the hetero-interfaces was investigated by means of photoluminescence (PL) and transmission electron microscopy (TEM). The difference between the cases using TBP and PH 3 was described, focusing on the waiting time dependence of the hetero-interface quality. The PL FWHM measured at 4.2 K was as small as 6.1 meV with optimized growth conditions, and the TEM images also proved excellent hetero-interfaces of the MQW structure grown with TBAs and TBP. InGaAs/InGaAsP separate confinement heterostructure 3 QW lasers grown by entire organic source MOVPE (EOS-MOVPE) had a threshold current density of 710 A/cm 2, an internal loss of 15 cm -1 and an internal quantum efficiency of 70%.

Low power all-optical polarisation gate switch in a passive InGaAsP MQW waveguide at 1.53 µm

Optimised design of an InGaAsP multiquantum well waveguide has allowed the demonstration of all-optical switching of a 30 ps pulse with coupled peak powers of 350 mW. This is achieved at 1.53 µm using resonant bandfilling and plasma effect refractive nonlinearities.

Engineering of barrier band structure for electroabsorption MQW modulators

The introduction of tensile strain to the barriers of InGaAsP multiquantum well, λ = 1.55 µm, electroabsorption modulators is proposed. It decreases the valence band barrier height, and heavy hole escape time, which greatly increases the optical saturation intensity leading to smaller, lower capacitance modulators with greater power handling capabilities.

Strained InGaAsP multiquantum wells for optical electroabsorption waveguide modulators

The quantum-confined Stark effect in strained InGaAsP multiquantum wells with InGaAsP barriers and its application to the optical electroabsorption waveguide modulator are described. A large spectral red shift of more than 450Å is observed at a low applied voltage of 3V. An extinction ratio of &gt;14dB is demonstrated with a driving voltage as low as 5V.

Fabrication and performance characteristics of 1.55-μm InGaAsP multiquantum well ridge guide lasers

We report the fabrication and performance characteristics of InGaAsP ridge waveguide lasers with multiquantum well (MQW) active layers emitting near 1.55 μm. The active region has four active wells (1.55 μm InGaAsP) and three barriers (1.3 μm InGaAsP). The thicknesses of the active wells and the barrier layers are ∼250 Å. The 360-μm-long lasers have threshold currents in the range 60–80 mA at 30 °C, external differential quantum efficiency ∼25% at 30 °C, and T0∼70 K. The modulation bandwidths of the lasers are ∼1.5 GHz and they exhibit less frequency chirping than similar lasers with conventional double heterostructure (DH) active layer. Since frequency chirp limits the performance of high bit rate long haul fiber communication system at 1.55 μm, we believe MQW lasers offer an advantage over conventional DH lasers.

Gain measurements in InGaAsP multiquantum well lasers

This letter reports the polarization dependence and temperature dependence of gain spectrum in InGaAsP multiquantum well (MQW) lasers emitting at 13 μm. The gain of the TE mode is larger (by ∼40 cm−1) than that of the TM mode. The peak gain for the TM mode is shifted towards shorter wavelengths from that of the TE mode. This is because both light hole and heavy hole transitions contribute to TE emission whereas the TM emission is principally due to light hole transitions. The large gain difference between the TE and TM mode suggests that the occurrence of stress induced effects (e.g., light-current kinks) may be reduced in MQW active layer lasers. The net gain G is found to vary linearly with the injection current I. The slope dG/dI of the gain-current curve for these MQW lasers decreases with increasing temperature. However, the decrease is considerably smaller than that for conventional InGaAsP double heterostructure lasers. The smaller decrease is consistent with the observed lower temperature dependence of threshold (high T0) of the MQW lasers.

Fabrication and performance characteristics of InGaAsP multiquantum well double channel planar buried heterostructure lasers

We report the fabrication and performance characteristics of InGaAsP double channel planar buried heterostructure (DCPBH) lasers with multiquantum well active layers emitting at 1.3 μm. These lasers have threshold currents in the range 40–50 mA at 30 °C, external differential quantum efficiencies of ∼50% at 30 °C, and T0 values ∼160–180 K in the temperature range 10–60 °C. Under optical pumping the measured T0 are in the range 100–150 K. The lasers operate in a single transverse mode up to high powers (&amp;gt;10 mW/facet), can be modulated at ∼2 Gb/s, and exhibit less frequency chirping than similar lasers with conventional active layers. The observed high T0 and smaller chirp make DCPBH multiquantum well lasers potentially attractive for system applications.