Buried Heterostructure Laser Fabrication Research Articles

Low-dislocation-density, nonplanar GaN templates for buried heterostructure lasers grown by lateral epitaxial overgrowth

We report here the formation of nonplanar GaN templates, which consist of low-dislocation-density, naturally grown GaN ridge mesas, as a mean to facilitate the fabrication of buried heterostructure lasers. Defect reduction is realized by introducing a two-step lateral epitaxial overgrowth procedure that utilizes dislocation bending in the formation of pyramidal mesas to eradicate the threading dislocations that originate from a planar buffer layer. Transmission electron microscopy and atomic force microscopy indicate a mesa top facet having low defect density (∼8×107cm−2), atomic flatness (∼0.29nm mean roughness). Our demonstration has opened the possibility of forming buried heterostructure lasers on nonplanar GaN templates.

Total in situ etching and regrowth in an MBE system: application to buried heterostructure lasers

A new chlorine-based chemical beam etching technique (CBET) has been combined with molecular beam epitaxy (MBE) technology to prepare InP-InGaAsP buried heterostructures in a total in situ etching and regrowth process for the first time. This novel processing technology, combining two techniques in the same MBE growth chamber, is very attractive for the realization of high-performance discrete or integrated optoelectronic devices. The different aspects of the etching process optimization are reviewed in the case of InP-InGaAsP heterostructures, and a first application to buried heterostructure laser fabrication is presented. The results obtained for buried ridge stripe (BRS) lasers are very promising and compare favorably to the state-of-the-art lasers. This first device application passes a milestone in the development of this new technology and demonstrates its potential for further applications to the fabrication of optoelectronic devices.

Molecular beam epitaxy of laterally structured lead chalcogenides for the fabrication of buried heterostructure lasers

Buried heterostructure (BH) lasers with active layers of PbSe, PbEuSe, PbSrSe and PbSnSe were made using molecular beam epitaxy (MBE). After growing the active layer the growth was interrupted. By use of photolithography and Ar+ ion beam etching, mesa stripes were defined and overgrown by a second MBE step. The overgrowth was investigated employing scanning electron microscopy (SEM). A selective chemical etch was used to resolve areas of different composition. The SEM pictures indicate the crucial role of the mesa shape and surface quality for the overgrowth process. Sharp edges result in deep cracks or grooves beside a well grown ridge. The authors successfully employed a chemi-mechanical polish after the ion milling process. The obtained smooth mesa shape results in a better overgrowth. As an alternative approach for fabrication of BH lasers shadow-masked growth of the active mesa stripe was investigated. Masks with slits in the 15 mu m range and sharp edges were obtained by anisotropic etching of (100)Si BH lasers with an active stripe width of 20 mu m were made by this technique and showed a threshold current comparable to double heterostructure (DH) lasers. Lateral structuring improved BH laser far-field distributions compared with DH lasers. The observed far-fields can be explained by a waveguide model.

A novel technique for low-threshold and high-power InGaAs/GaAs strained-layer 0.98-μm buried heterostructure laser fabrication

A novel fabrication technique has been developed for InGaAs/GaAs strained-layer buried heterostructure lasers. Dielectric masks and Zn diffusion are not required in this technique. This novel fabrication process is much easier than the conventional approach and yields excellent laser results. A low threshold of 3 mA and high-power operation for lasing wavelength of 9800±20 Å have been achieved with graded index separate confinement heterostructure devices using this novel technique.

A novel technique for GaInAsP/InP buried heterostructure laser fabrication

A simple fabrication technique for GaInAsP/InP buried heterostructure lasers has been developed based on a newly observed mass transport phenomenon on chemically etched InP mesas. Threshold currents as low as 9.0 mA have been obtained.