T. Taniwatari

InGaAs/InGaAsP MQW electroabsorption modulator integrated with a DFB laser fabricated by band-gap energy control selective area MOCVD

The fabrication and basic characteristics of a InGaAs/InGaAsP multi-quantum-well (MQW) electroabsorption modulator with a novel structure integrated with a distributed-feedback (DFB) laser are presented. A fundamental study was performed on the applicability of the InGaAs/InGaAsP MQW structure to an electroabsorption-type modulator. Efficient attenuation small hole pileup and small chirp characteristics of a discrete modulator based on this MQW structure were demonstrated experimentally. A study of the controllability of in-plane band-gap energy by the use of selective-area metal-organic chemical vapor deposition (MOCVD) was also demonstrated. The modulator was monolithically integrated with a MQW DFB laser of the same material. Using a low-capacitance semi-insulating buried heterostructure, over 14 GHz modulation under high-light-output operations up to +10 dBm was achieved. Modulation at 10 Gb/s with a modulation voltage swing of only 1 V/sub pp/ demonstrates the potential value of this system for 1.55- mu m lightwave communications. >

Detuning adjustable multiwavelength MQW-DFB laser array grown by effective index/quantum energy control selective area MOVPE

A multiwavelength MQW DFB laser array with novel structure Is described. Oscillation wavelength and gain peak wavelength were simultaneously controlled on the same epitaxial wafer by using modulated grown thicknesses of selectively grown InGaAs/InGaAsP/InP MQW active waveguides. The laser array with constant-pitch built-in corrugation fabricated by a simple DFB laser process demonstrated 10.1 nm controllable range for lasing wavelength and 45 nm for gain peak wavelengths, with uniform lasing properties and narrow spectral linewidths. The technique is attractive for light sources used in WDM/FDM applications.<<ETX>>

Anti‐phase direct bonding and its application to the fabrication of InP‐based 1.55 μm wavelength lasers on GaAs substrates

We propose anti‐phase direct bonding and report on the first demonstration of its application to device fabrication. Cross‐sectional observation by high‐resolution transmission electron microscope showed that InP and GaAs wafers bonded at the atomic level and the misfit dislocations were localized at the bonding interface. Then InP‐based 1.55 μm wavelength lasers were fabricated on GaAs. The performance of the lasers was approximately equal to that of the lasers formed by in‐phase direct bonding. Moreover, stable operation was possible for more than 1000 h at 50 °C.

1.24–1.66 μm quantum energy tuning for simultaneously grown InGaAs/InP quantum wells by selective-area metalorganic vapor phase epitaxy

For the purpose of achieving a wide variety of photonic integrated circuits application, optimum selective mask design in selective-area metalorganic vapor phase epitaxy (MOVFE) is experimentally investigated in order to obtain multiple quantum well (MQW) layers with wide bandgap controllable range and with high optical crystal quality. Dependence of compositional change and layer flatness on mask size was systematically examined for selectively grown InGaAs/InF layers. We found that the open space width between SiO 2 stripes is a key design parameter for obtaining uniform distribution of thickness and good characteristics in photoluminescence. The open space width was therefore optimized to be 10 μm or more in our growth conditions, which is much larger than the effective surface migration length and smaller than the vapor phase diffusion length of group III species. Based on this mask design, we demonstrated an extremely wide quantum energy tuning range of 253 meV for simultaneously grown InGaAs/InF MQW structures. High luminescence efficiency was maintained throughout the tuning range

1.3-/spl mu/m InGaAsP-InP n-type modulation-doped strained multiquantum-well lasers

The use of n-type modulation doping to reduce the threshold current, the carrier lifetime, and the internal loss in 1.3-/spl mu/m InGaAsP-InP strained multiquantum-well (MQW) lasers is experimentally demonstrated. The threshold current density, the carrier lifetime, and the internal loss were reduced by about 33%, 36%, and 28%, respectively, as compared with an undoped MQW laser. Moreover, the turn-on delay time in the n-type modulation-doped MQW lasers with a low-leakage buried heterostructure was reduced by about 35%. These results confirm the suitability of this type of laser for use in the basic structure of a monolithic laser array used as a light source for high-density parallel optical interconnection.

Threading dislocation reduction in InP on GaAs by thin strained interlayer and its application to the fabrication of 1.3-μm-wavelength laser on GaAs

This paper examines the reduction of threading dislocation by a thin strained interlayer (SIL), and a long-wavelength laser fabricated on a GaAs substrate with SILs. A cross-sectional transmission electron microscope is used to observe the dislocation blocking ability of an SIL made of InGaP, which is inserted in an InP layer grown on a GaAs substrate. The characteristics of the BH laser emitting at 1.3 µm on GaAs are investigated. Most of them are improved by SIL insertion. In particular, threshold current is reduced to 70% on average and is also distributed more uniformly.

Comparison of Relaxation Process of Compressive and Tensile Strains in InGaAs Lattice-Mismatched Layers on InP Substrates

This paper investigates the difference in crystal quality between strained-layer multiple quantum wells with compressive (+0.5%) and tensile strains (-0.5 %). For the compressive strain, the photoluminescence intensity decreased and the length of fringe bending increased from 250 A to 500 A when the number of periods increased from 5 to 15. The amount of fringe bending increased when the InP thickness decreased, especially when the strain was compressive. We also investigated the relaxation process in an InGaAs layer as a function of the layer thickness (from 25 nm to 2 µ m). For a compressive strain (+1.1%), misfit dislocations were observed near the interface between InGaAs and InP substrate. On the other hand, for a tensile strain (-1.1 %), we observed cracks instead of misfit dislocations. Moreover, the cracks were considered to increase the X-ray full width at half maximum of both the InGaAs lattice-mismatched layer and the InP substrate.

Reduced turn-on delay time in 1.3-μm InGaAsP-InP n-type modulation-doped strained multiquantum-well lasers with a buried heterostructure

A reduction in both the threshold current and carrier lifetime is demonstrated, for the first time, in an n-type modulation-doped InGaAsP strained multiquantum well laser with a buried heterostructure. Threshold current and carrier lifetime is reduced by 10% and 15%, respectively, as compared with a undoped MQW laser, which results in a 35% decrease in the turn-on delay time. This confirms the suitability of this type of laser for use as a light source for high-density parallel optical interconnection.

In Situ X-Ray Monitoring of Metalorganic Vapor Phase Epitaxy

We demonstrate the in situ X-ray monitoring of metalorganic vapor phase epitaxy by using a four-crystal monochromator. The in situ X-ray measurement of InGaAs with a thickness of 0.3 µm on an InP substrate was achieved even under growth conditions at 620°C. Moreover, this monitoring technique is not affected by the atmosphere of the reactant source gasses. Also, the X-ray peak of the InGaAs at 300°C, is clearly separated from the InP peak in spite of the small lattice mismatch (-0.09%) without aligning the wafer. The dependence of lattice mismatch on temperature measured by this X-ray monitoring technique agrees with the dependence calculated theoretically. This technique can also be used to measure the thickness dependence of lattice mismatch and temperature dependence of in-plane compressive strain for InP on GaAs heteroepitaxy.

High-quality Zn-diffused InP-related materials fabricated by the open-tube technique

We evaluate, for the first time, the crystal quality of a Zn-diffused thick In/sub 0.76/Ga/sub 0.24/As/sub 0.55/P/sub 0.45//InP structure created by the open-tube technique. We also investigate the intermixing at the heterointerface of a Zn diffused In/sub 0.47/Ga/sub 0.53/As/InP multiple quantum well structure.