Toshinari Fujimori

Weakly Index Guided Buried-Stripe Type 980 nm Laser Diodes Grown by a Combination of Gas Source Molecular Beam Epitaxy and Metalorganic Vapor Phase Epitaxy with an AlGaAs/InGaP/GaAs Double Etch Stop Structure

In order to fabricate weakly index guided buried-stripe type 980 nm laser diodes (LDs) precisely and reproducibly, we have developed a novel double etch stop (DES) structure which consists of AlGaAs/InGaP/GaAs layers. By employing the DES structure, an effective refractive index step (Δneff) of 3.6×10-3 and a waveguide bottom width (Wb) of 2.2 µm were realized to maintain a stable transverse mode. The LDs were fabricated by a combination of gas-source molecular beam epitaxy (GS-MBE) and metalorganic vapor phase epitaxy (MOVPE) on a 2-inch wafer and showed uniformly high performance, especially in the region within a 15.5 mm radius from the center. A high kink level of 315±15 mW was achieved. Considering wafer uniformity, we estimated that Δneff and Wb should be controlled to about 3.6×10-3± 3.5×10-4 and 2.22±0.06 µm, respectively, under the condition of a vertical optical confinement factor \varGamma\fallingdotseq1.16%/well. We have also confirmed the high quality of the entire process, including the DES method, by employing a reliability test at 200 mW light output power up to 2500 h.

Reliability improvement of 980 nm laser diodes with a new facet passivation process

A newly developed facet passivation method producing highly reliable, high output power 980 nm InGaAs MQW laser diodes (LDs) is described. Even with facet cleavage in air, the devices exhibit a maximum output of 500 mW. Aging tests at 200-250 mW showed very good performance.

Layer-by-layer growth mechanism of AlxGa1-xP grown by gas-source MBE

Abstract The layer-by-layer growth process of AlxGa1-xP (0≦x≦1) was investigated by observing the reflection high energy electron diffraction intensity oscillations of the samples during growth. The damping of the oscillations were examined and it was found that there were three stages in the damping process. The damping behavior depended on the Al composition. Gallium-rich compositions (x = 0.23 and 0.37) had a smaller damping rate than that of GaP. Aluminum-rich compositions (x > 0.5) clearly showed the three stages in the damping process, and the observed number of oscillations decreased with increasing Al composition. We propose a model for the growth process of AlxGa1-xP. For Ga-rich compositions the layer-by-layer growth is enhanced by Al atoms, which reduce the average terrace size. For Al-rich compositions, where nucleation dominates, the surface roughness is diminished by Ga atoms which migrate and fill the kink-sites.