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Research of the Weber Group

The objective of our research is the analysis and control of defects in semiconductors to improve our fundamental understanding of these defects and to ultimately improve the performance of electronic and opto-electronic semiconductor devices. We perform thin film growth by MBE, processing of simple device structures in the UC microlab, and in-depth structural, electrical, optical and magnetic resonance characterization of semiconductor materials and device structures. Most projects involve collaborations with industry.

Our research group is organized in four teams, with most teams including a postdoctoral scientist or Research Associate, graduate students and undergraduate aids.

For an overview, see E.R. Weber's ICDS talk.

XBIC Map of a multicrystalline solar cell material 1. Silicon

Research of the Si team is currently concentrated on the study of transition metal contamination and radiation damage in Si crystals and device structures for IC and photovoltaic applications. Our research on Si for IC applications is part of the Silicon Wafer Engineering and Defect Science (SiWEDS) consortium. The research on Si for photovoltaic applications is part of a team of University groups sponsored by the National Renewable Energy Lab (NREL). Part of this research is performed at the synchrotron in LBNL (Advanced Light Source, ALS).

Further info:
Dr. Andrei Istratov istratov@socrates.berkeley.edu.

2. GaAs and related compounds

The research of this team is concerned with the growth and analysis of thin films of GaAs and GaAsN, most of them grown by MBE. One topic of great interest has been the investigation of GaAs deposited by MBE at low temperature, down to 200°C (Low temperature grown -GaAs). This material has a high concentration of excess As that results in ultrashort carrier lifetime and semi-insulating properties. Doped LT-GaAs can have carrier concentrations much higher then usually possible in GaAs grown by MBE at higher temperatures. Recently, the research interest of this team turned to the deposition of In(Ga)As quantum dot structures and (In)GaAsN layers with small bandgap for applications in the optical communication area (1.3 and 1.5 µm). Another focal point are defects formed upon oxidation of ultrathin layers of AlAs.

Further info:
Dr. Petra Specht, specht@socrates.Berkeley.EDU

3. Wide-bandgap semiconductors

This research team concentrated on the investigation of GaN thin films, InGaN quantum wells, and recently ZnO nanowire structures for blue and white light emitting devices and high-speed optoelectronics. Studies of MBE growth of GaN on different substrates and with novel buffer layers is part of this research. An important issue of recent interest is the quantitative analysis of the influence of polarization-induced charge separation and inhomogeneity-induced charge localization in InGaN/GaN quantum well structures for commercial blue and white LEDS.

Further info:
Dr. Petra Specht, specht@socrates.Berkeley.EDU

STM image of a Te donor  on the GaAs surface 4. Scanning tunneling microscopy

We are studying III/V semiconductors and semiconductor heterostructures by cross-sectional scanning tunneling microscopy (X-STM) and STM-induced cathodo-luminescence (STM-CL). The STM-CL studies are done in a system that allows investigations down to LHe temperature.







[Seminar ]