Toshio Ito

Influence of phosphorus vapor ambient for InGaAsP growth on GaAs substrate

For visible‐light‐emitting laser diodes, InGaAsP double heterostructures have been grown on GaAs substrates using liquid‐phase epitaxy. As the growth temperature is as high as about 780u2009°C, a large amount of phosphorus evaporates from the solutions for the cladding layers during the growth process. The phosphorus vapor disturbs the solution composition for the active layer, so that very thin and uniform active layers cannot be obtained. By using In‐P‐Sn solution and supplying the phosphorus partial pressure around the graphite boat, the influence of phosphorus vapor ambient for InGaAsP (λPL=805 nm) growth is confirmed. When the phosphorus partial pressure increases, the surface of epitaxial layer becomes rough and the substrate is partly etched back. From x‐ray diffraction and photoluminescence spectral measurements, the composition of the grown layer is also found to be changed. As a result of increasing the flow rate of H2 gas in order to protect the solution for the active layer from phosphorus contami...

A simple method for monolithic fabrication of InGaAsP/GaAs lasers

A simple method for the fabrication of Fabry–Perot mirrors of InGaAsP/GaAs lasers is presented. The vertical and smooth wall etching is done for active layers only (not for both active and cladding layers), by an H2SO4:H2O2:H2O=3:1:1 etchant for 2–5 s. Since the active layers are much thinner than the cladding layers, the etching becomes much easier. The threshold current density of the etched mirror laser is ∼4.4 kA/cm2, about 1.1 times that of the cleaved laser, and the mirror reflectivity is evaluated as 29.4% (cleaved 31.4%).

Lasing characteristics of 0.8‐μm InGaAsP/GaAs lasers fabricated by wet chemical etching

0.8‐μm InGaAsP/GaAs stripe lasers, in which cavity mirrors were formed by two‐step wet chemical etching, have been fabricated monolithically. The laser resonators were aligned along the 〈011〉 and the 〈010〉 directions. The first etching was done in 5% Br methanol. The secondary etching was done in H2SO4:H2O2:H2O (3:1:1 by volume) etchant for the active layers only, and gave low threshold lasers. Their threshold current densities were compared with those of the cleaved‐mirror lasers made from the same wafer. Some longitudinal lasing modes were observed in the wavelength range of 805–810 nm. The characteristic temperature T0 was 116 K in the temperature range 28–87u2009°C. The relationship between the state of the etched facets and the near‐ and far‐field patterns was examined. It was found that this two‐step etching technique for the laser mirrors is very suitable for aligning the lasers along desirable directions on the same wafer for monolithic integrated optical circuits.

AlGaAs burying growth for InGaAsP/GaAs buried heterostructure lasers by liquid-phase epitaxy

Abstract Liquid-phase-epitaxial (LPE) growth of Al x Ga 1− x As layers at 700°C has been used in the fabrication of 0.8 μ m InGaAsP buried heterostructure (BH) lasers grown on GaAs substrates. The solidus composition, X , was 0.66. By etching the mesa in KKI solution at 3°C for 2 min after a mesa etch in Br-methanol solution, high quality BH wafers with smooth surfaces and interfaces were reproducibly obtained after the AlGaAs secondary BH growth. The InGaAsP active region was entirely surrounded by InGaAsP cladding layers and AlGaAs burying layers providing both lateral and vertical carrier and optical confinement. Lasing action at room temperature under pulsed operation was achieved.