Intermixing the wells and barriers of quantum-well (QW) laser heterostructures generally results in an increase in the bandgap energy and is accompanied by changes in the refractive index. A technique, based on ion implantation-induced QW intermixing, has been developed to enhance the quantum-well intermixing (QWI) rate in selected areas of a wafer. Such processes offer the prospect of a powerful and simple fabrication route for the integration of discrete optoelectronic devices and for forming photonic integrated circuits.

Photonic integrated circuits fabricated using ion implantation

In this topical review, the potential of the focused ion beam (FIB) technology and ultimate applications are reviewed. After an introduction to the technology and to the operating principles of liquid metal ion sources (LMIS), of ion optics and instrument architectures, several applications are described and discussed. First, the application of FIB for microcircuit inspection, metrology and failure analysis is presented. Then, we introduce and illustrate some advanced patterning schemes we propose as next generation FIB processing examples. These patterning schemes are (i) local defect injection or smoothing in magnetic thin film direct patterning, (ii) functionalization of graphite substrates to guide organization of clusters, (iii) local and selective epitaxy of III‐V semiconductor quantum dots and (iv) FIB patterned solid-state nanopores for biological molecules manipulation and analysis. We conclude this work by giving our vision of the future developments for FIB technology. (Some figures in this article are in colour only in the electronic version)

https://iopscience.iop.org/article/10.1088/0268-1242/24/4/043001/pdf

Focused ion beam technology and ultimate applications

InGaAs/GaAs/AlGaAs and InGaAs/InGaAsP/InP laser structures, with InGaAs quantum wells approximately 1.85 μm beneath the surface, were implanted with ions having energies up to 8.6 MeV. Intermixing of the quantum wells, after rapid thermal annealing, was monitored through changes in the energy, linewidth, and intensity of the photoluminescence peak from the quantum wells. Where the defects had to diffuse primarily through Al0.71Ga0.29As, these quantities correlate strongly, for short anneal times, with calculated vacancy generation and ion deposition at the depth of the quantum well prior to annealing. This suggests that the defect diffusion length in the AlGaAs and/or GaAs is quite low. For diffusion primarily through InP, the photoluminescence data correlated well with the calculated total number of vacancies created in the sample, suggesting that defect diffusion is very efficient in InP.

Defect diffusion in ion implanted AlGaAs and InP: Consequences for quantum well intermixing

By focused ion beam implantation induced thermal intermixing the bandgap of quantum-well layer structures can be selectively changed. This allows lateral bandgap engineering and gives a new degree of freedom for lateral structuring. The principle technological aspects like the dependence of the bandgap shift on implantation parameters and the spatial resolution are investigated and applied to the fabrication of photonic and optoelectronic devices. Lateral waveguiding in InP-based materials, the possibility of monolithic integration of bandgap shifted waveguide areas into active devices and the improvement of the lateral carrier confinement in ridge waveguide lasers are demonstrated. Due to the high spatial resolution, modulated bandgap gratings could be realized with periods down to 90 mn. These bandgap gratings were used to create gain-coupled distributed-feedback lasers in different material systems with well controlled single-mode emission.

Y.P. Hu

Papers

Optical study of GaAs/GaAlAs quantum structures processed by high energy focused ion beam implantation