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Microwave Solid State Power Devices Yonglai Tian.

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Presentation on theme: "Microwave Solid State Power Devices Yonglai Tian."— Presentation transcript:

1 Microwave Solid State Power Devices Yonglai Tian

2 Introduction of microwave power devices Performance of Si and GaAs microwave devices Wide bandgap semiconductors for microwave applications Processing of WBG silicon carbide wafers SiC microwave power devices GaN microwave power device

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4 Various types of microwave power devices Magnetron Traveling wave tube Klystron Gyrotrons

5 Disadvantages Large size Heavy Fixed frequency Complicated power supply (HV) Poor quality of waveform spectrum Slow tuning and coupling Cost Single mode cavity for Microwave sintering of advanced ceramics

6 Multiple DoD platform will benefit from microwave solid state devices and WBG semiconductors

7 Electrodeless HID lamps driven by microwaves 1400w magnetron driven HID lamps, 200w aperture HID lamps (7mm) driven by solid state microwave devices

8 Various types of microwave solid state devices Bipolar Junction Transistors (BJT) –Si BJT –HBT (hetero junction bipolar transistor) AlGaAs-GaAs HBT SiGe-Si HBT Field Effect Transistors –GaAs MESFET (metal-semiconductor field effect transistors) –HEMT (high electron mobility transistors)

9 Various types of microwave solid state devices Wide Bandgap Transistors –SiC SIT (static induction transistors) MESFET (metal-semiconductor field effect transistors) HBT (hetero junction bipolar transistor) –GaN HEMT (high electron mobility transistors)

10 Introduction of microwave power devices Performance of Si and GaAs microwave devices Wide bandgap semiconductors for microwave applications Processing of WBG silicon carbide wafers SiC microwave power devices GaN microwave power device

11 Performance characterization Out put power P max P max V max x I max –V max: Voltage breakdown –I max : Heat removed, gate width and length Power Density PD PD = V max x Current density –V max: Voltage breakdown –Current density: limited by bandgap and thermal conductivity

12 Performance characterization Frequency f max (V s /L) –Vs. saturated carrier velocity –Gate length P ma α 1/f 2 Efficiency PAE Depends on wave shape, impedance, leakage current and power gain

13 Widely used Si microwave devices Si BJT – < 5 GHz – W at 1 GHz –> 40% Efficiency –Low cost Limitation: –P max : voltage breakdown and current (limited by emitter periphery and resistivity of epitaxial layer) –f : limited by carrier mobility, capacitance C bc A typical Si BJT characteristics –Frequency; GHz –Output power: 105 W –Pulse width: 50 m –Duty cycle: 10% –Gain: 6.5 db (min) –Efficiency:40% (min) –Supply voltage: 40V

14 GaAs MESFET (Metal semiconductor field effect transistors) GaAs MSFET –3-30 GHz –Power density: w/mm –Power level and cost: Frequency band Power (W) cost ($) C and S Ku Limitation: –f and P max : gate length, thermal conductivity

15 HEMT and HBT HEMT (High electronic mobility transistor) AlGaAs-GaAs heterojunction – GHz –High frequency –High P max –High efficiency –Low noise HBT (heterojunction bipolar junction transistor) Similar to BJT, but much higher power and frequency performance

16 State of the art power output performance

17 State of the art power density performance

18 State of the art PAE performance

19 Evolution of microwave device noise figures

20 Introduction of microwave power devices Performance of Si and GaAs microwave devices Wide bandgap semiconductors for microwave applications Processing of WBG silicon carbide wafers SiC microwave power devices GaN microwave power device

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25 Advantages of wide bandgap semiconductors (SiC, GaN and diamond) 1.Wide bandgap –SiC: 3.2 eV –GaN: 3.4 eV –Si : 1.1 eV –GaAs: 1.4 eV 3 times higher than that of Si and GaAs –High service temperature of 650 o C due to the high intrinsic temperature –Low noise

26 Advantages 2.High breakdown voltage –SiC: 10 times higher than that of Si and GaAs –High output power due to high V –High operating frequency –Short-channel MESFETs in SiC F max : 50 GHz

27 Advantages 3. High thermal conductivity –SiC 4.9 w/(C-cm) 10 times higher than that of Si and GaAs –Si: 1.6 w/(C-cm) –GaN 0.5 w/(C-cm) 4.High Saturated velocity –SiC 2.2 x10 7 m/s 2 times higher than that of Si and GaAs –Si and GaAs: 1 x10 7 m/s

28 Physical characteristics of Si, GaAs and main wide bandgap semiconductors

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31 WBG semiconductor material challenges

32 Introduction of microwave power devices Performance of Si and GaAs microwave devices Wide bandgap semiconductors for microwave applications Processing of WBG silicon carbide wafers SiC microwave power devices GaN microwave power device

33 Growth of SiC single crystal J. A. Lely, Philips Labs 1955 sublimation process for growing a- SiC crystals Davis at North Carolina State University (NCSU), 1987 seeded- growth sublimation process Cree Res, started in 1987 by students from the NCSU. Cree, 1990, Introduction of 25 mm single crystal wafers of 6H-SiC 1990

34 Physical vapor transport (PVT) growth of SiC single crystal wafers PVT growth process: –Evaporation of SiC charge materials –Transport of vapor spices to the growth surface –Adsorption surface diffusion and incorporation of atoms into crystal. –Temperature: o C – T of 10-30C controlled by moving RF coil –Growth rate controlled by T and pressure in reactor

35 Defects in SiC wafer Micropipes– breakdown at low voltage Dislocations Low angle grain boundaries Stacking faults

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37 GMU WBGS research projects: Ion implantation of SiC wafers Ion implantation is the only viable selective area doping techniques for SiC device production N and P were implanted in p-type and Al and B were implanted in n- type 6H-SiC using single and multiple ion energy schedules ranged from 50 KeV to 4 MeV Second ion mass spectrometry measurements (SIMS) were conducted to obtain the implant depth profiles Doping layer theickness.

38 N-implanted SiC (50 KeV to 4MeV at 700 o C)

39 B-implanted SiC (50 KeV to 4MeV at 700 o C)

40 Multiple energy P-implanted SiC

41 Rapid annealing of ion implanted SiC The crystal lattice is damaged by the penetration of ion energetic ions Post annealing is necessary to recover the lattice damage Microwave and conventional annealing at 1500C –Microwave: Heating rate; 200 o C/min, total time: 20 min. –Conventional: heating rate: 10 o C/min, total time 3 hr. Rutherford backscattering (RBS) measurements are conducted before and after ion-implantation to study the recovery of the crystal lattice.

42 RSB spectra on N-implanted SiC

43 Sheet resistivity of annealed SiC wafers GMU data

44 Sheet resistivity of nitrogen-implanted 4H- SiC as a function of time and temperature. Sheet resistivity of phosphorus -implanted 4H- SiC as a function of time and temperature.

45 Best Reported Sheet Resistivity of Ion Implanted SiC Figure 1. Sheet resistivity of nitrogen implants into 6H silicon carbide at room tmperature. Figure 2. Sheet resistivity of Al implants into 6H silicon carbide at room tmperature

46 Introduction of microwave power devices Performance of Si and GaAs microwave devices Wide bandgap semiconductors for microwave applications Processing of WBG silicon carbide wafers SiC microwave power devices GaN microwave power device

47 SiC microwave power devices High power 4H-SiC static induction transistors (SITs) –Vertical short channel FET structure –Current flow vertically by modulating the internal potential of the channel using surrounding gate structure –Characteristics similar to a vacuum-tube tiode –470W (1.36 /mm) at 600 MHz –38 W (1.2 w/mm) at 3 GHz –PAE ~ 47%

48 High power 4H-SiC static induction transistors (SITs) Measured static I-V characteristics of a SIT Cross section of a SiC SIT SEM photo of a SIT device. The mesa fingers are 1 µm wide and 100 µm long. The total mesa length is 1 cm (100 fingers).

49 The best performance –High output power; 900 W (at 1.3 GHz, drain efficiency = 65%, gain = 11 dB) [Northrop-Grumman/ Cree Inc] –High frequency performance with a cut-off frequency of 7 GHz [Purdue] A comparison of SIT with other relevant SiC microwave devices..

50 High power SiC MESFET Three epitaxial layers –P buffer layer –Channel layer doped N d =3x10 17 cm -3 –Heavily doped n+ cap layer Performance –P max : 15W –Frequency: 2.1 Ghz –Power density: 1w/mm –PAE; 54% a

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52 Cross section of SiC MESFET. The epitaxial layers were grown on a semi-insulating SiC substrate, including p-buffer layer and a n- doped channel layer

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54 Introduction of microwave power devices Performance of Si and GaAs microwave devices Wide bandgap semiconductors for microwave applications Processing of WBG silicon carbide wafers SiC microwave power devices GaN microwave power device

55 GaN Power High electronic mobility transistors two dimensional electron gas with a high mobility is formed at the AlGaN-GaN heterojunction interface, the mobility can be in excess of 1000 cm 2 /Vs High frequency 100GHz High power density: 10w/mm Base station microwave power amplifier highly linear mixers high power switches

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