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Deep Level Transient Spectroscopy (DLTS)

Related products: MFIA, MF-IA, HF2TA, HF2LI

Deep Level Transient Spectroscopy Application Diagram using the Zurich Instruments MFIA Impedance Analyzer

Application Description

DLTS is a powerful and commonly used technique to investigate both the concentration and carrier binding energy of defects in semiconductors. The technique essentially involves measuring capacitance transients at different temperatures. The semiconductor junction is initially reverse biassed to deplete the bulk of mobile charge carriers, then as the reverse bias voltage is briefly set to zero by a positive voltage pulse, the empty traps are filled. After the pulse, the junction is again reverse biassed and the charges are gradually emitted causing a change in capacitance. The resulting capacitance transients can be measured by the MFIA with high time resolution and over a long period to capture the full transient.

Measurement Strategies

  • The Zurich Instruments MFIA can measure the capacitance transient at frequencies ranging from 1 mHz to 5 MHz (not just at 1 MHz), on a time scale of 10 us (at 1 MHz). The Data acquisition module of LabOne, the Zurich Instruments control software, can be triggered either by the external pulse generator, or the internally generated bias pulse. With this DAQ module, the whole transient can be reliably captured at high time resolution and for long-rate windows, including the steady-state before the trigger event thanks to the data buffer.
  • In addition, the dual channel lock-in amplifier included in the MFIA can be used to capture the current transient along with the capacitance transient. This can be done on a faster time-scale than capacitance measurements, but does not include information of the absolute capacitance.

The Benefits of Choosing Zurich Instruments

  • The MFIA offers measurement solutions for both measurement strategies, simultaneously.
  • The MFIA can be considered a superior alternative to the discontinued Boonton 7200, thanks to the integrated digitizer, wider capacitance measurement range and flexible working frequency. Furthermore, it offers numerous software tools such as a plotter and sweeper to monitor and optimize your experiment.
  • The MFIA has an eight-stage current input stage, so the instrument is not overloaded when the reverse bias pulse is applied.
  • The MFIA interface software, LabOne includes a scope to capture the fast signals such as the demodulated current and voltage simultaneously on one scope window.
  • The powerful APIs included with the MFIA allow integration of the MFIA into complex lab set-ups, and control of temperature via analog IN/OUT.
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