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ECE 662 Microwave Electronics Transferred Electron Devices February 10, 2005 Two-Terminal Negative Resistance Devices Transferred Electron Device Operation (TED) Review of Carrier Transport Review of Carrier Transport Drift Velocity vs. Electric Field Silicon at Room Temperature Ref. Sze Drift Velocity vs Electric Field Ref Sze High Field Transport in n-type GaAs Negative Differential Resistance in n-type GaAs Measured velocity-field characteristics Ref Sze Review of Carrier Transport Transferred Electron Device Operation (TED) Transferred Electron Device Operation (TED) Electron accumulation in the Presence of Negative Differential Resistivity (NDR) Ref: Liao Gunn Diode Eventually, the process evens out and velocities are equal. Space charge than drifts to anode end and the process repeats. v d 12 2 Drift time L/v d R or Ln 0 10 cm e _ n0 e _ where _ is the negative differenti al mobility. These are Transit ti me modes. - one domain at a time must clear out. f 1/T v d /L 1/ t ; v d 107 cm / sec f not affected by the external circuit. Dipole Layer in Negative Differential Resistivity (NDR) Ref: Liao (a) To (d) Electric field vs. distance during one ac cycle at Four intervals, a to d. e) Voltage and Current wave Forms of a Transit time Domain mode. Ref. Sze Gunn Domain Modes Ref Liao Numerical simulation of the timedependant behavior of cathodenucleated TED for the transit-time domain mode. Each successive time is 24ps. ref. Sze Gunn Domain Modes Ref Liao Numerical simulation of the timedependant behavior of cathodenucleated TED for the quenched domain mode. Each successive time is 24ps. ref. Sze Biasdependent RF characteristics of a D-band InP TED Mechanical tuning characteristic for the D-band InP TED close to maximum bias Typical Structures and Doping Profiles for TED Devices Ref. Sze Solid-State Device Power Output vs Frequency ref: Sze and modified by Tian State-of-the Art RF Power Levels for TED under CW operation ref. Sze Summary of Transferred Electron Devices - 1 Ref: Golio (2003) • Widely used in oscillators from the microwave through high mm-wave frequency bands. • Good RF output power capability (mW to W level) • Moderate efficiency (20%) • Excellent noise and bandwidth capability Summary of Transferred Electron Devices - 2 Ref: Golio (2003) • Fabricated at low cost • Excellent price-to-performance ratio, for example, most common oscillator device used in police automotive radars • Many commercially available solid-state sources for 60 to 100 GHz (for example, automotive collision-avoidance radars) often use InP TEDs.