Research Interests:

As device dimensions are reduced to the nanometer scale length, the physics and chemistry of the processes used in their fabrication become an inextricable determinant of their ultimate performance. The research in my group centers about the study of novel nanometer-scale structures and devices, and the low-damage, high spatial resolution processes that are required for their formation. In addition, we look towards ways of integrating heterogeneous materials within device structures by techniques that ensure high quality interfaces. Two particular projects are described in greater detail:
In collaboration with Atac Imamoglu and other researchers at UCSB, we have been utilizing strongly coupled quantum dot-cavity interactions as a possible basis for quantum information processing (quantum computation). Low-damage formation of microdisk structures with embedded quantum dots (grown by Molecular Beam Epitaxy) has resulted in record cavity Q¹s in excess of 18,000, and optically-pumped lasing has been demonstrated for high-Q optical modes. Further reduction of the volume of the resonator (cavity) can produce high-Q structures that would be coupled to single quantum dots; such small-volume resonators have been formed in the Œdefects¹ of photonic bandgap (PBG) structures etched in to GaAs/AlGaAs materials. The PBGs comprise ~250 nm holes separated by 250 nm. The maximum Q values for our initial measurements have been ~ 12,000. We are working to better control the sizes and placements of the critical features and quantum dots in these structures.
The demands of structural and size uniformity, as well as control of placement of nanoscale components poses huge challenges for more Œconventional¹ means of fabrication, involving a succession of lithographic and pattern transfer steps. Biogenic approaches appear to offer solutions to those challenges, if a suitable, broad set of biological-inorganic building blocks can be identified. Accordingly, we have embarked on a program with Angela Belcher at UT Austin and other collaborators to identify such peptide building blocks through a combinatorial approach, utilizing phage display libraries reacted with a variety of (opto)electronic and magnetic substrate materials. The preliminary results have identified peptide sequences that are not only specific to the particular chemical composition of a substrate (e.g. GaAs, as opposed to Si), but also to a particular crystal orientation of a material (e.g. GaAs (100), as opposed to GaAs (111)A). Further work will explore the basis of the selectivity, as well as simple applications of assembly, using the specific peptide-inorganic affinities.

Selected Publications:

• "Selection of peptides with semiconductor binding specificity for directed nanocrystal assembly," S.R. Whaley, D.S. English, E.L. Hu, P.F. Barbara, A. M. Belcher, Nature 405, 665-668
• "Laser emission from quantum dots in microdisk structures," Michler, P.; Kiraz, A.; Zhang, L.; Becher, C.; Hu, E.; Imamoglu, A., Appl. Phys. Lett., 77 (2), p.184-6 (July 2000)
• "Channeling as a mechanism for dry etch damage in GaN," Haberer, E.D.; Ching-Hui Chen; Abare, A.; Hansen, M.; Denbaars, S.;Coldren, L.; Mishra, U.; Hu, E.L., Appl. Phys. Lett., 76 (26), p.3941-3 (June 2000)
• "Improvement of the interface quality during thermal oxidation of Al0.98Ga0.02As layers due to the presence of low-temperature-grown GaAs", Ferrer, J.C.; Liliental-Weber, Z.; Reese, H.; Chiu, Y.J.; Hu, E., Appl. Phys. Lett., 77 (2), p.205-7 (July 2000)
• "Characterization of high-quality InGaN/GaN multiquantum wells with time-resolved photoluminescence", M.S. Minsky, S.B. Fleischer, A.C. Abare, J.E. Bowers, E.L. Hu, S. Keller, S.P. DenBaars, Appl. Phys. Lett 72(9), 1066-1068 (March 1998).

Biography:

Before joining UCSB in 1984, Professor Hu worked at AT&T Bell Laboratories, developing microfabrication and nanofabrication techniques to facilitate the study of superconducting and semiconducting devices and circuits. She has continued those research themes at UCSB, through a variety of collaborative efforts, examining processes critical for the fabrication and operation of superconducting, electronic and optical devices. In particular, she has focused on ion-assisted chemical etching techniques having high spatial resolution, photo-driven processing tuned to the unique optical properties of the materials, and passivation treatments to enhance optical and electrical properties of structures at submicron dimensions. She has studied the formation of high quality, heterogeneous interfaces, such as those between semiconductors and superconductors, oxide and semiconductor, or two non lattice-matched semiconductors. She is currently serving as Director of QUEST, the NSF Science and Technology Center for Quantized Electronic Structures. She as well directs Nanotech, the UCSB component of the NSF National Nanofabrication Users Network. She has served as Vice Chair (1989-92), and subsequently Chair (1992-94) of the ECE Department. She received the Tau Beta Pi Outstanding Faculty Award in ECE for 1989-90. Professor Hu is a Fellow of the APS and IEEE. In 1995, she was awarded an honorary Doctor of Engineering from Glasgow University.