C. Starck

Lateral modulations in zero‐net‐strained GaInAsP multilayers grown by gas source molecular‐beam epitaxy

Compressive GaInAsP multiple quantum wells (MQW) grown by gas source molecular‐beam epitaxy present altered structural and optical characteristics when tensile GaInAsP barriers are used instead of lattice‐matched ones. An alternate tensile/compressive GaInAsP MQW has been examined by transmission electron microscopy. A strong lateral modulation of thickness, strain, and probably chemical composition was shown. This modulation exhibits pronounced anisotropy, with a periodicity of about 50 nm along the [110] direction. Although its origin is not fully accounted for yet, it seems to allow partial elastic relaxation of tensile layers. Based on this analysis, a schematic description of distortion modulation is proposed.

Gas source molecular beam epitaxy of alternated tensile / compressive strained GaInAsP multiple quantum wells emitting at 1.5 μm

Abstract Compressive and tensile strained GaInAsP layers as well as zero-net strain multiple quantum wells, grown by gas source molecular beam epitaxy, have been investigated. Reflection high energy electron diffraction patterns show two-dimensional growth for compressive strained layers ( Δa a . Three-dimensional growth is observed after a few nanometers for tensile strained layers even for low tensile value ( Δa a . Transmission electron microscopy shows that three-dimensional growth of a tensile strained layer is related to a quasi-periodic composition modulation along the [110] in the epitaxial plane.

High-purity InP grown by gas source molecular beam epitaxy (GSMBE)

Abstract The growth of high purity indium phosphide by gas source molecular beam epitaxy (GSMBE) using solid indium source and pure phosphine is reported. 77 K mobilities as high as 112,000 cm 2 /V·s with residual carrier concentrations of 2 × 10 14 cm -3 have been obtained. 4.2 K photoluminescence spectra are dominated by free-exciton and neutral donor-exciton transitions. Very weak acceptor related transitions show a low compensation ratio for this sample.

Direct measurement of lateral elastic modulations in a zero‐net strained GaInAsP/InP multilayer

A zero‐net strained GaInAsP/InP(001) multilayer grown by gas source molecular beam epitaxy exhibits large interfacial undulations and an orthorhombic modulated distortion, which are attributed to elastic relaxation of tensile layers. It is examined by high resolution transmission electron microscopy in order to directly determine the strain distribution in the (110) plane. The interplanar spacings are found to be laterally modulated along the [110] direction within tensile and compressive layers. The interplanar spacing modulation is perfectly correlated to the interfacial morphology. Therefore, the strain is not homogeneous but concentrated along [110] oriented lines. Large variations of (110) interplanar spacings up to 3.5% have been measured, while the lattice mismatch between tensile and compressive layers is only 2%. The observed strain distribution is qualitatively consistent with an elastic relaxation mechanism of the tensile layer. Different other effects are reviewed. Surface relaxation effects...

Strained quaternary GaInAsP quantum well lasee emitting at 1.5 μm grown by gas source molecular beam epitaxy

Abstract Quantum well structures and separate confinement heterostructure lasers based on strained quaternary Ga 1− x In x As 1− y P y well material were grown by gas source molecular beam epitaxy. The substitution of As for P allows a simultaneous control of wavelength, well width and strain in the structure. Single strained layers in InP show photoluminescence with narrow linewidth (4 to 8 meV). Broad area lasers with strained and unstrained layers have been grown with five quantum wells and identical optical confinement. The strained quaternary structure has a threshold current density of 760 A/cm 2 for L = 400 μm, an internal quantum efficiency of nearly 100%, a waveguide loss of 10 cm -1 and a high T 0 value ( T 0 = 91 K). Single-well structures have a lowest value of 240 A/cm 2 for 3 mm long devices.

Low spectral chirp and large electroabsorption in a strained InGaAsP/InGaAsP multiple quantum well modulator

An intensity modulator based on the quantum confined Stark effect with strained InGaAsP quantum wells and InGaAsP barriers was grown using gas source molecular beam epitaxy. The highest electroabsorption effect and the first estimation of the spectral chirp ever reported with such a modulator under TE polarization mode around 1.55 μm were obtained. The attenuation was measured to be better than −30 dB with a reverse driving voltage lower than 3 V and the phase‐amplitude coupling factor has been estimated to be lower than 0.2 over a large operating wavelength range.

High temperature (Ga)InAsP/high band gap GaInAsP barriers 1.3 μm SL-MQW lasers grown by gas source MBE

We report on an experimental investigation of the temperature sensitivity of (Ga)InAsP compressively strained multi-quantum well (MQW) 1.3 μm broad area lasers with respect to the amount of strain and barrier band gap. The composition of wells are adjusted to let the strains range from 0.6% to 1.4%, whereas barrier band gap scales from 1.13 to 1.3 eV. Threshold current densities per well for infinite length as low as 60 to 135 A cm -2 at 20°C asses for the high quality of the structures grown by gas source MBE. Characteristic temperatures of 80 to 110 K, depending on the barrier band gap, are measured between 20°C and 80°C for 1200 μm long devices.

Well-size dependence of electro-optic effects in GaInAsP/InP quantum wells grown by GSMBE

Wannier-Stark and quantum confined Stark effects are demonstrated in GaInAs/InP and GaInAsP/InP quantum well structures grown by gas source molecular beam epitaxy. The structures are characterized by photoluminescence and photocurrent spectroscopy. The analysis of the absorption edge of wells of different sizes shows that wide GaInAsP wells are preferable for the realization of QCSE absorption modulators at 1.55 μm. A blue shift of 16 meV under an electric field of 20 kV/cm has been observed in a GaInAs/InP Wannier-Stark structure.

Buried heterostructure laser fabricated using three‐step gas source molecular beam epitaxy

Buried heterostructure lasers fabricated using a three‐step gas source molecular beam epitaxy (GSMBE) process are presented for the first time. We propose a new structure design compatible with nonselective regrowth for the blocking layers, therefore avoiding the use of a dielectric mask. The structure is terminated by a second overgrowth after a material lift‐off. Preliminary results show cw operation with threshold currents of 60 mA for 800‐μm‐long devices and maximum output power up to 27 mW per facet.

Lateral thickness modulations in alternate tensile–compressive strained GaInAsP multilayers grown by gas source molecular beam epitaxy

Abstract Compressive GaInAsP multiple quantum wells (MQWs) grown on (001) InP have demonstrated high potential for the production of lasers emitting at 1.5 μm. A GaInAsP tensile barrier is now used instead of a lattice matched barrier to compensate for the compressive strain. However, zero-net strained MWQs grown at 500° by gas source molecular beam epitaxy show a decrease in structural and optical quality. A structural investigation of two MQWs using a – 0.5% mismatched barrier was performed using transmission electron microscopy to understand why using a tensile barrier induces such degradation. All the samples studied show a lateral quasi-periodic thickness modulation which is strongly anisotropic with a periodicity of about 50 nm along the [110] direction, while no modulation occurs along the [110] direction. Since the growth is easier on relaxed areas than on strained areas, we deduce that the thicker parts of the layer are more relaxed than the thinner parts. Moreover, the average period of 50 nm is found to be independent of both the barrier thickness and the mismatch of the compressive well, while the amplitude of the modulation is drastically enhanced when the barrier thickness increases. This confirms that the phenomenon is controlled by the partial elastic relaxation of tensile layers.