AVS 47th International Symposium
    Semiconductors Friday Sessions
       Session SC+EL-FrM

Invited Paper SC+EL-FrM8
Probing Nanoscale Electronic Properties in Nitride Semiconductor Heterostructures

Friday, October 6, 2000, 10:40 am, Room 306

Session: III-Nitride Processing and Devices
Presenter: E.T. Yu, University of California, San Diego
Authors: E.T. Yu, University of California, San Diego
K.V. Smith, University of California, San Diego
X.Z. Dang, University of California, San Diego
Correspondent: Click to Email
III-V nitride heterostructures are of outstanding current interest for both optoelectronic and electronic device applications. However, the high concentrations of point and extended defects typically present even in device-quality nitride semiconductor material necessitates detailed characterization and understanding of local structure and electronic properties at atomic to micron length scales for optimization of device performance. In particular, the presence of a variety of defect structures in combination with strong piezoelectric and spontaneous polarization effects in nitride semiconductors leads to pronounced variations in local electronic properties. Experimental characterization, theoretical analysis, and numerical simulation of these effects, especially in the context of nitride heterostructure field-effect transistor (HFET) structures, will be described. Scanning capacitance microscopy has been used extensively to characterize local electronic structure in AlGaN/GaN HFET structures. Measurement and analysis of capacitance contrast as a function of bias voltage allows submicron-scale lateral variations in transistor threshold voltage, nanoscale depleted regions within the channel of the transistor in the vicinity of negatively charged threading dislocations, and evidence of piezoelectric fields arising from local strain in the vicinity of dislocation lines to be observed. Application of large bias voltages during the imaging process is found to give rise to localized trapping of charge in deep levels. Measurement and analysis of the resulting contrast allows the distribution of trapped charge both laterally and as a function of depth to be probed.