Vacancy enhanced compositional mixing of quantum well (QW) structures induced by ion beam implantation has shown itself to be a useful technique for achieving spatially selective tuning of the QW bandgap. As QWs form the active region of most optoelectronic devices, this method is being actively pursued as a means of monolithically integrating many such components onto a single substrate. This work presents a novel variation on this technique allowing one to deliver several times the maximum QW bandgap shift traditionally attributed to a single implant/RTA (rapid thermal anneal) cycle. This is achieved by distributing the total implanted ion dose over multiple sequential ion implantation and RTA cycles. Continuous-wave photoluminescence (CWPL) measurements are used to monitor the extent of QW intermixing taking place, and demonstrate the success of this innovation in various material systems (GaAs/AlGaAs, InGaAs/GaAs, InGaAs/InP). In another experiment, the effectiveness of high energy (8 MeV As$\sp{4+})$ implantation in intermixing GRINSCH (graded-index separate confinement heterostructure) QW laser structures grown in InGaAs/GaAs was demonstrated. Preliminary investigations were carried out on the effects of sample temperature, and ion current density during implantation on the intermixed QWs. Results from CWPL measurements suggest that better quality intermixed material can be obtained by implanting at elevated sample temperatures, and low ion current densities. Finally the effect of ion implantation induced intermixing on the effective radiative lifetimes in GaAs/AlGaAs quantum wells is investigated using the technique of time-resolved photoluminescence (TRPL). Below the critical dose (required to initiate disordering), the carrier lifetimes appear enhanced by the processing although no changes are discernible in the CWPL spectra. Above the critical dose, carrier lifetimes are reduced by residual defects created in the intermixed wells by the implantation procedure. These observations reflect the greater sensitivity of TRPL in detecting residual damage produced by intermixing QW material over CWPL.
| Identifer | oai:union.ndltd.org:uottawa.ca/oai:ruor.uottawa.ca:10393/9697 |
| Date | January 1996 |
| Creators | Piva, Paul Garrett. |
| Contributors | Charbonneau, Sylvain, |
| Publisher | University of Ottawa (Canada) |
| Source Sets | Université d’Ottawa |
| Detected Language | English |
| Type | Thesis |
| Format | 65 p. |
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