Keiji Takaoka

Low-threshold and high-temperature operation of InGaAlP-based proton-implanted red VCSELs

InGaAlP-based red vertical-cavity surface-emitting lasers (VCSELs) are attractive light sources for plastic optical fiber (POF)-based low-cost and high-speed data links, because the POF has a low-loss window around the 650-nm wavelength region, and VCSELs are suitable for high-speed modulation and can be treated easily as is the case for LEDs. We have fabricated InGaAlP-based red VCSELs using the proton-implanted planar structures, and realized continuous-wave (CW) operation up to 60/spl deg/C with the lasing wavelength of 666 nm and the threshold current of 2.5 mA.

New selective metalorganic chemical vapor deposition growth method for InAlAs with high aluminum composition

Abstract Selective growth was achieved for the pair of InAlAs and successively deposited InP when the InAlAs thickness was of the order of several nanometers even under growth conditions where thick InAlAs could not be grown selectively. The “critical thickness” of InAlAs for the selective growth of InP/InAlAs was found to be of a certain value in the range of 40 to 100 nm. This “critical thickness” was mainly determined by the total InAlAs thickness, but increased slightly with an increase of the diffusion duration of precursor adatoms of InAlAs on a SiO 2 mask. Although the thickness of several nanometers was very small, it was confirmed to be sufficiently large to attain a large band gap and current blocking enhancement effect of InAlAs in the p-n junction. When a thin layer of In 0.4 Al 0.6 As was inserted into a laser diode current blocking layer, an improvement of the laser diode temperature characteristics was confirmed.

High-temperature operation and thermal analysis of InGaAlP-based oxide-confined red VCSELs

We successfully fabricated high-performance oxide-confined red VCSELs. A low threshold current of 0.5 mA and an extremely high maximum CW lasing temperature of 75C were achieved with a room-temperature lasing wavelength of 666 nm. This low-threshold and high-temperature operation was realized, because the oxide-confined structure is advantageous for making smaller devices, compared to the proton-implanted structure.

Step bunching of InP caused by heavy doping of Se in metalorganic chemical vapor deposition and its application to device fabrication

We have found that step bunching occurs in heavily Se doped InP, grown by MOCVD, for both [001] and (111)B planes and that it occurs with a lower Se source gas flow rate for the (111)B plane than for the [001] plane. Using this heavy Se doping, we have successfully fabricated novel planar buried heterostructure lasers on p-InP substrates, in which the Se-doped n-InP current blocking layer does not make contact with the n-InP cladding layer.