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HBT Collector Characterization by the Spectral Photocurrent Technique
Fritz SCHUERMEYER Peter J. ZAMPARDI Sharon FITZSIMMONS Roger E. WELSER Noren PAN
IEICE TRANSACTIONS on Electronics
Publication Date: 2001/10/01
Print ISSN: 0916-8516
Type of Manuscript: Special Section PAPER (Joint Special Issue on Heterostructure Microelectronics with TWHM 2000 (Topical Workshop on Heterostructure Microelectronics 2000))
Category: III-V HBTs
photoluminescence, HBT, GaAs, AlGaAs, InGaP,
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Photoelectric techniques, such as photoluminescence are commonly used to evaluate and qualify heterostructure materials. These studies provide invaluable information on the energy configuration of these devices. In this paper, we extend photoelectric techniques to the evaluation of fully fabricated HBTs. We describe photoconduction measurements performed on the base/collector junctions in GaAs based HBTs. The devices studied contained a window in the emitter metal and monochromatic, chopped light was focused through a microscope into the window. The measurements are performed on wafer at room temperature. The spectral characteristic of the photocurrent provides information on the material and allows the determination of the source of the measured photocurrent. The dependence of the photocurrent on the junction bias allows the profiling of the junction. Three different collector structures were investigated, containing GaAs, AlGaAs, and InGaP. The effects of electron and hole barriers are evaluated. The information obtained allows for the design of improved HBTs.