Speaker: Mattias Hammar
Time: 14:00, June. 1st.
Location: SIST 1D-402
Host: Prof. Baile Chen
Abstract:
Increasing demands for advanced networking services and other high-end photonics applications put harsh requirements on versatile and high-performance optical components. Nanostructuring and heterogeneous integration here plays an enabling role since it allow for precise tuning and optimization of the optoelectronic device properties. Here we review some developments at our lab during the recent years related to photonic-crystal membrane-reflector VCSELs and photonic band edge VCSELs in the InP system and discuss the prospects for high-speed operation, CMOS integration and low-cost manufacturability [1-5]. In a different development, we consider quantum dot (QD)-based single-photon telecommunication-wavelength emitters in the GaAs-system. Using graded InGaAs buffer layer we realize InAs QDs in an In-rich InGaAs metamorphic matrix grown on GaAs substrate and observe narrow and bright micro-photoluminescence emission lines from isolated QDs around 1.55 µm at low temperature [6]. By tuning the MOVPE growth conditions, almost perfectly symmetrical QDs can be realized for minimized fine-structure splitting [7]. These QDs offer an interesting alternative approach to InAs/InP QDs for the realization of single-photon emitters for the telecommunication regime. Besides optical communication, we also address work related to detectors for long-wavelength infrared (LWIR; 8-12 µm) imaging. Such detector elements are presently predominantly realized in the mercury-cadmium-telluride (MCT) system, which offers high performance but suffers from difficult growth and materials properties and thereby high cost, and AlGaAs/GaAs quantum-well infrared photodetectors (QWIPs), which offers excellent manufacturing properties over large wafers and thereby low cost but at compromised performance levels. Here we report on the development of interband quantum dot photodetectors based on spatially indirect transitions in the In(Ga)Sb QD/InAs type-II system to combine the excellent performance of MCT detectors with the manufacturing properties of QWIPs. This approach resembles that of strained-layer quantum-well InAs/GaSb superlattice detectors but with relaxed epitaxial growth complexity [8] and performance advantages due to inherent type II QD properties [9]. Finally, we describe our recent efforts to fabricated LWIR Type-II Strained-Layer Superlattice (T2SL) detectors using metal-organic vapor-phase epitaxy (MOVPE), which would have some clear manufacturing advantages over the present molecular-beam epitaxy (MBE) paradigm.
Bio:
Prof. Mattias Hammar is a Professor in Electrical Engineering at KTH. His career includes roles in both academia and industry, including the Swedish Institute of Microelectronics, IBM Research Division, and Zarlink Semiconductor, and he has expertise in photonic materials and devices. He is Deputy Director of the Advanced Chip Technologies Competence Center (ACT) and Program Director for KTH’s International Master’s Program in Nanotechnology.
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