Cross-sections and electron distributions relating to hot electron impact excitation efficiencies

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Spatial control of quantum well intermixing in GaAs/AGlaAs using a one-step process

Dielectric cap disordering with strontium fluoride masking is used to provide a range of bandgap values in GaAs/AlGaAs quantum wells using a single annealing step. Partial area coverage by a strontium fluoride mask under a silica cap determines the amount of quantum well intermixing

Low-loss extended cavity lasers by dielectric cap disordering with a novel masking technique

Low-loss extended cavity lasers fabricated in GaAs/AlGaAs quantum-well material busing silica cap disordering and strontium fluoride selective area masking are described. Losses as low as 17 dBcm/sup -1/ were measured in the passive slab waveguide sections. Lasing action was achieved in devices with passive sections of up to 2 mm in length

Fabrication of multiple wavelength lasers in GaAs-AlGaAs structures using a one-step spatially controlled quantum-well intermixing technique

We have applied a new technique, based on impurity-free vacancy diffusion, to control the degree of intermixing across a wafer. Bandgap tuned lasers were fabricated using this technique. Five distinguishable lasing wavelengths were observed from five selected intermixed regions on a single chip. These lasers showed no significant change in transparency current, internal quantum efficiency or internal propagation loss, which indicates that the material quality was not degraded after intermixing

A comparison of carbon and zinc doping in GaAs/AlGaAs lasers bandgap-tuned by impurity-free vacancy disordering

Bandgap tuning by impurity-free vacancy disordering was investigated on carbon and zinc p-doped laser structures. Zinc diffused during annealing and consequently only carbon-doped material lased. After annealing, threshold current densities rose from 225 to 255 A cm-2 due to an increase in the transparency current; the gain constant of the quantum wells remained constant

The application of the selective intermixing in selected area (SISA) technique to the fabrication of photonic devices in GaAs/AlGaAs structures

We demonstrate the fabrication of multiple wavelength lasers, and multi-channel wavelength division multiplexers using the one-step 'selective intermixing in selected area' quantum well intermixing technique in GaAs/AlGaAs structures. This technique is based on impurity-free vacancy diffusion and enables one to control the degree of intermixing across a wafer. Lasers with the bandgaps tuned to five different positions have been fabricated on a single chip. These lasers showed only small variations in transparency current, internal quantum efficiency and internal propagation loss, which indicates that the quality of the material remains good after being intel mixed. Four-channel wavelength demultiplexers or waveguide photodetectors have also been fabricated. Photocurrent and spontaneous emission spectra from individual diodes showed the shift of the absorption edge by different degrees due to the selective degree of quantum well intermixing. The results obtained also demonstrate the use of this technique in the fabrication of broad wavelength emission superluminescent diodes

Single-mode operation of a surface grating distributed feedback GaAs-AlGaAs laser with variable-width waveguide

Single-mode distributed feedback laser operation can be achieved by introducing an appropriate phase jump within the feedback grating, causing lasing to occur within the stop-band. One possible approach involves variation of the waveguide stripe width in an index-guided structure, in conjunction with a grating of uniform periodicity. If the phase change is allowed to accumulate over a sufficient length of the width perturbed stripe waveguide, a /spl lambda//4 shift can be realized. We report the first laser of this type using a surface grating structure with only postgrowth processing

Suppression of quantum well intermixing in GaAs/AlGaAs laser structures using phosphorus-doped SiO2 encapsulant layer

A phosphorus-doped silica (SiO2:P) cap containing 5 wt% P has been demonstrated to inhibit the bandgap shifts of p-i-n and n-i-p GaAs/AlGaAs quantum well laser structures after rapid thermal processing. The intermixing suppression has been attributed to the fact that SiO2:P is more dense and void free compared with standard SiO2 together with a strain relaxation effect of the cap layer during annealing. Band gap shift differences as large as 100 meV have been observed from samples capped with SiO2 and with SiO2:P. The n-i-p structure showed a higher degree of intermixing compared to p-i-n structure. This behaviour has been attributed to the rise of Fermi level in the n doped structure, through which the formation energy of Ga vacancies is reduced compared to the p doped structure