Integration of photonic devices has been the subject of much research interest in recent years due to its implications for optical communication systems. However, the development of the fabrication processes involved in photonic integration has not been trivial due largely to the diversity in functions and consequently modes of operation of various photonic devices. Because of these requirements, many photonic device structures have poor compatibility for monolithic fabrication. There is an important need to develop better large scale manufacturable processes to facilitate photonic integration. We propose to investigate ion mixing as a process for planar integration of photonic devices made of quantum-well and superlattice structures. As a processing technique, ion mixing offers many advantages: (i) the process can be carried out at sufficiently low temperatures to allow for a self-aligned process, (ii) metallic ion masks for self-alignment purposes can serve as electrodes for devices, (iii) readily available noble gas ions are just as efficient as shallow dopant ions with similar atomic mass in causing disordering, and (iv) judiciously chosen ions can be used to induce disordering and to improve device isolation simultaneously. However, there are several issues that need to be resolved before ion-mixing becomes a useful process for photonic integration. The first issue is to understand the mixing process at a microscopic level so as to relate the intermixing of semiconductor materials and their properties such as bandgap, optical index, with or without strain involved. The second has to do with the material damage caused by ion-irradiation which can affect both the transport and the optical properties. Approaches to reduce this damage to a level acceptable to photonic integration will be investigated in this study. The third issue is to study how ion-mixing can be used in the formation of laser waveguide, a critical component of photonic technology. A fourth issue is to investigate the use of ion mixing in the improvement of heterojunction bipolar transistors. To address these issues, the proposed program has the following objectives: (i) investigation of process control of ion mixing, particularly the reduction of ion irradiation damage to a level acceptable for photonic devices, (ii) the planarization of devices by ion mixing with an initial (2) goal if fabricating planar stripe index guided lasers, and (iii) monolithic device integration by ion mixing, driving toward modulator/laser and laser/HBT integration.
