Y. Kawai

Heteroepitaxial growth of InP on a GaAs substrate by low‐pressure metalorganic vapor phase epitaxy

Good quality InP was successfully grown on (100)GaAs 2° off normal toward [011] substrates by introducing low‐temperature grown GaAs/InP double buffer layers. It was found that addition of a thin GaAs buffer layer (20 nm thick) grown at low temperature (430 °C) between the GaAs substrate and an InP buffer layer was effective for improving the crystal quality. The full width at half‐maximum of the x‐ray rocking curve was as narrow as 200 arcsec for a 6‐μm‐thick InP layer. An electron mobility of 15 000 cm2/(V s) at 77 K was obtained for an unintentionally doped layer. The intensity of the photoluminescence at 77 K was as good as that for an InP substrate.

High power output, low threshold, inner stripe GaInAsP laser diode on a p‐type InP substrate

A V‐grooved, inner stripe laser diode on a p‐type InP substrate emitting at 1.3 μm is reported. The maximum cw output power of 65 mW and the threshold current of 15 mA with fundamental transverse mode operation are performed. The laser has high differential quantum efficiency of 70% at 20 °C and is stably operated at high temperatures; output power >20 mW at 80 °C. The dependence of the threshold current density on the doping impurity level of zinc in the active layer is also discussed.

High‐power and high‐speed 1.3 μm V‐grooved inner‐stripe lasers with new semi‐insulating current confinement structures on p‐InP substrates

A significant improvement in the maximum output power of a 1.3 μm GaInAsP/InP laser with a semi‐insulating current confinement structure is reported. The improvement has been achieved by interposing an n‐type InP layer between a p‐InP substrate and an Fe‐doped InP layer. A maximum cw output power of 180 mW and a modulation bandwidth of 8.5 GHz have been obtained.

Method of generating nearly transform-limited pulses from gain-switched distributed-feedback laser diodes and its application to soliton transmission

A train of nearly transform-limited pulses are generated from a 1.55-microm distributed-feedback laser diode by using gain switching in a novel technique, which is a combination of a spectral window and temporal compression. By amplifying these pulses with erbium-doped fiber amplifiers, we demonstrate soliton transmission in a conventional single-mode fiber.

High‐power and high‐speed semi‐insulating blocked V‐grooved inner‐stripe lasers at 1.3 μm wavelength fabricated on p‐InP substrates

A maximum cw power of 90 mW at 25 °C was obtained for a GaInAsP/InP laser with a semi‐insulating InP current blocking layer grown by metalorganic vapor phase epitaxy on a p‐type InP substrate, a 700‐μm‐long cavity, and an antireflection coating on the front facet. The 3 dB bandwidth was in excess of 6 GHz with a low parasitic capacitance of 15 pF despite the long cavity. The semi‐insulating layer with the resistivity of 5×107 Ω cm was formed by doping only Fe. The current blocking characteristics of the blocking layer with the same configuration as the lasers were examined under various temperatures.

Hetero-epitaxial growth of InP on Si substrates by LP-MOVPE

Abstract A novel hetero-epitaxial technique for growing good quality InP layers on Si (100) 2° off normal toward [011] substrates has been developed. The key element of this process is introducing a thin GaAs buffer layer (10–20 nm) at a low temperature (430°C) followed by a thin InP buffer layer (10–20 nm) at low temperatures (400–550°C). The layers grown by this technique show a single domain structure, a narrow X-ray full width at half maximum (250 arc sec), a narrow spectral linewidth of photoluminescence at 77 K (10.5 meV) and a relatively low etch pit density ((1–2)×10 7 cm −2 ).

V‐grooved inner‐stripe laser diodes on a p‐type substrate operating over 100 mW at 1.5 μm wavelength

An output power of 110 mW cw has been achieved with a V‐grooved inner‐stripe laser diode on a p‐type substrate emitting at 1.5 μm wavelength. Output powers over 100 mW could be obtained by determining the appropriate cavity length and the reflectivity of the front mirror facet, a parameter that depends heavily on output power. These lasers were fabricated without introducing anti‐meltback layers. The meltback problem of the active layer was overcome using a low‐temperature liquid phase epitaxy technique.

Degradation of GaAs0.9P0.1 light‐emitting diodes for optical fiber communication with internal stress

Degradation mechanisms of GaAs0.9P0.1 light‐emitting diodes for optical fiber communication systems were studied to elucidate the effects of internal compressive stress (on the order of 107–108 dyn/cm2) on initial rapid degradation. The diodes were fabricated from wafers with various phosphorus composition gradients (?0.7%/μm) in the tapered layer.Experimental results from the degradation of the diodes operating at 660 A/cm2 showed that the lifetimes of the diodes increased with decreasing the compositional grading in the crystals. The improved lifetime is due not only to the suppression of 〈110〉 dark‐line defects but also to the slow growth velocities of 〈100〉 dark‐line defects and due to slow accumulation rates of nonradiative recombination centers near the PN junctions at low internal stress. For the first time, the growth velocities of 〈100〉 dark‐line defects during initial rapid degradation were observed to depend on the internal compressive stress.

Widely tunable semiconductor optical fiber ring laser

A wide tunable optical fiber ring laser with a diffraction grating as a tuning element is demonstrated. A wide tuning range over 100 nm is achieved using a high performance traveling‐wave amplifier (TWA) as a gain medium. The TWA with a V‐grooved inner stripe structure on a p substrate (VIPS structure) has a high peak gain over 30 dB and a broad gain width of 100 nm at 16 dB. The effects of the gain of TWA and the total loss of the external ring cavity on the tuning range are also discussed.

Interfacial layers of InP/Si heteroepitaxy

Abstract In the heteroepitaxial growth of InP on Si by metal organic vapor phase epitaxy, the structural properties of the interfacial layers were investigated using scanning electron microscopy, Auger electron spectroscopy and Rutherford back-scattering spectrometry. The interfacial layers consisting of the first GaAs buffer layer (≈ 15 nm thick) and the second InP buffer layer (≈ 15 nm thick) grown at low temperatures (430–550°C) play a significant role as buffer layers to alleviate the large lattice mismatch of 8% between InP and Si. We have found that better crystallinity of InP device layers could be obtained by depositing the InP buffer layer on a slightly migrated GaAs buffer layer than on an as-grown GaAs buffer layer.