T his program consists of the development of viable processing methods for gallium nitride and related compounds. A systematic study of etching techniques, ohmic contact formation, and other metallizations will be conducted.

This project focuses on experimental issues for the fabrication of novel optoelectronic devices and circuits in gallium nitride and related materials. UV detectors, field effect transistors, and heterojunction bipolar transistors will be investigated. Methods for integrating these devices will also be explored.

This program consists of fabricating and characterizing high-speed optical and electronic devices. Novel advanced microelectronic processes are used to fabricate MSM photodetectors and modulation-doped transistors with submicrometer critical dimensions in various III-V compound semiconductors. The final objective of this work is the realization of wide bandwidth (;mt20 GHz) integrated optoelectronic receiver circuits.

This program is an experimental investigation on the design and characterization of high-speed metal-semiconductor-metal (MSM) photodetectors working at long wavelengths (1.3 and 1.55 ;gmm). The influence of nanometer-scale metal gratings and variations in the photon-absorbing layer on the speed will be investigated. The utility of transparent conductors as the electrodes will also be investigated.

Ultralow-dimensional structures, such as quantum wires or quantum dots, characterized by transverse dimensions below 100 nm may constitute the next generation of very sophisticated semiconductor devices. This research is aimed at investigating the potential of these artificial systems for VLSI and high-speed applications. This effort involves the fabrication and characteristics of low-dimensional structures as well as basic studies and modeling of their electronic and transport properties.

Scanning tunneling microscopy (STM) is being developed as a nanofabrication tool to extend electronic device fabrication into the sub-0.1 ;gm regime. This University Research Initiative is combining STM nanolithography with electron beam lithography, molecular beam epitaxy, dry processing, and silicon and III-V device fabrication to pursue this goal. To date, linewidths of 1 nm have been achieved on silicon surfaces using a unique ultrahigh vacuum (UHV) STM system constructed at the Beckman Institute. This capability is now being applied to fabricate devices that are controlled by quantum size effects.

Applications for microelectrical-mechanical systems (MEMS) that are being developed include low-cost microoptical mechanical switches for telecommunications, mechanical devices for microsurgery, and masks for biological molecule deposition. This project is aimed at high-force and displacement devices, as well as using dissimilar materials and creating 3-D utility from planar elements. One approach is to combine wafer-scale and laser-material processing to join elements which cannot be fabricated in the same process as silicon. Research in silicon and laser-material processing is currently being developed to solve the fundamental issues of MEMS.

This project is to develop processes for the fabrication of GaN/AlGaN laser structures. Various patterning schemes based on ion-assisted and laser-assisted etching will be investigated for the formation of laser facets.

This project seeks to understand temporal coherence in nanostructures and to determine the physical constraints for coherent electronic motion in future ultrahigh-speed devices. Both interferometric and spectroscopic measurements will be used to probe electronic wavepackets in fabricated GaAs/AlGaAs nanostructures.