1 An Introduction to Gallium Nitride (GaN) Device Characterization Steve Dudkiewicz, Eng Your Complete Measurement & Modeling Solutions Partner

2 - Introduction to GaN - Pulsed IV Measurements - Introduction to Load Pull - Pulsed-Bias Pulsed-RF Harmonic Load Pull - Thermal Infrared Load Pull Agenda

3 Viable enabling technology for high power amplifiers: -material maturity -yield improvement -expansion to 4” wafers -and inclusion of lower cost substrates GaN offers several advantages over other technologies: -higher operating voltage (over 100V breakdown) -higher operating temperature (over 150 o C channel temperature) -higher power density (5-30W/mm) GaN Technology

4 Problems associated with GaN: -the large output power capability → heat dissipation -trapping -self-heating -electrical performance degradation over time (threshold voltage, gate leakage current) Partial solution: -Pulsing bias minimizes self-heating -Choosing proper quiescent voltage minimizes trapping GaN Technology

5 Pulsed Measurements – System 1

6 Pulsed Measurements – System 2

7 DC- and Pulsed-IV Measurements

8 Impedance Control

9 The slide-screw tuner approach

10 Open loop active tuner approach

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12 x = source (s) or load (l) n = frequency band, e.g. baseband (0), fundamental (1) and harmonic (2 and up) = user defined reflection coefficient vs. frequency The wideband open loop active load-pull approach

13 Many higher-power GaN devices have source impedances around or below 1-5Ω because of their large peripheries Pulsed Source/Load Pull Load impedances are higher than source impedances, in the range of 3-15Ω

14 The following is an example of a 10W-linear power GaN device operating under compression at 25W where the fundamental impedance was kept constant at ZFo= 3Ω and the second harmonic impedance Z2Fo was swept across the entire Smith Chart. A variation of ~25% drain efficiency was observed while tuning 2Fo PAE=60% PAE=35% Harmonic Load Pull

15 Maury’s solution makes use of the triggering that is native to the pulsed-IV controller to trigger both the signal generator and power meter for accurate and reliable results. Pulsed Considerations 1) Bias Tees 2) Power Meter Average VS Peak 3) Triggering

16 Thermal IR Load Pull Max P out T hot_spot =212°C Max PAE T hot_spot =188.25°C - Compromise between Pout and PAE, using Temp to decide - Effect of poor match on temperature - Operating temperature in real-life conditions due to poor match

17 VSWR 3:1 in CW mode Pin_avail 28 dBm Pout dBm Gt 4.57 dB Vq_out 40 V Iq_out 1.99 mA Vq_in 3.55 mA Vout 40V Iout 351 mA Eff 8.39 % T hot_spot =284°C Pin_avail 28 dBm Pout dBm Gt dB Vq_out 40 V Iq_out 6.21 mA Vq_in 3.55 mA Vout 40V Iout 362 mA Eff % T hot_spot =181.5°C Pin_avail 28 dBm Pout dBm Gt 6.48 dB Vq_out 40 V Iq_out 9.06 mA Vq_in 3.55 mA Vout 40V Iout 415 mA Eff % T hot_spot =301°C T hot_spot =350°C

18 VSWR 3:1 in Pulse mode 130.4°C 124.5°C 114.6°C 109.6°C 109.3°C 110°C 122.6°C 139°C 148°C 151°C 153°C °C 151°C 147.8°C °C 134.6°C