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Microwave Solid State Power Devices Yonglai Tian. 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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slide2
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
various types of microwave power devices
Various types of microwave power devices

Magnetron

Traveling wave tube

Gyrotrons

Klystron

disadvantages
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

multiple dod platform will benefit from microwave solid state devices and wbg semiconductors
Multiple DoD platform will benefit from microwave solid state devices and WBG semiconductors
electrodeless hid lamps driven by microwaves
Electrodeless HID lamps driven by microwaves

200w aperture HID lamps (7mm) driven by solid state microwave devices

1400wmagnetron driven HID lamps,

various types of microwave solid state devices
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)
various types of microwave solid state devices1
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)
slide10
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
performance characterization
Performance characterization
  • Out put power Pmax

Pmax a Vmax x Imax

        • Vmax: Voltage breakdown
        • Imax: Heat removed, gate width and length
  • Power Density PD

PD = Vmax x Current density

        • Vmax: Voltage breakdown
        • Current density: limited by bandgap and thermal conductivity
performance characterization1
Performance characterization
  • Frequency

f maxa (Vs/L)

        • Vs. saturated carrier velocity
        • Gate length

Pmaα 1/f2

  • Efficiency PAE

Depends on wave shape, impedance, leakage current and power gain

widely used si microwave devices
Si BJT

< 5 GHz

100-600W at 1 GHz

> 40% Efficiency

Low cost

Limitation:

Pmax: 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; 2.7-2.9 GHz

Output power: 105 W

Pulse width: 50 mm

Duty cycle: 10%

Gain: 6.5 db (min)

Efficiency: 40% (min)

Supply voltage: 40V

Widely used Si microwave devices
gaas mesfet metal semiconductor field effect transistors
GaAs MESFET (Metal semiconductor field effect transistors)
  • GaAs MSFET
    • 3-30 GHz
    • Power density: 0.5-0.8 w/mm
    • Power level and cost:

Frequency band Power (W) cost ($)

C and S 10 300 20 600 30 900

Ku 10 1000 15 1500

  • Limitation:
    • f and Pmax: gate length, thermal conductivity
hemt and hbt
HEMT and HBT

HEMT (High electronic mobility transistor)

  • AlGaAs-GaAs heterojunction
    • 5-100 GHz
    • High frequency
    • High Pmax
    • High efficiency
    • Low noise

HBT (heterojunction bipolar junction transistor)

  • Similar to BJT, but much higher power and frequency performance
slide20
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
advantages of wide bandgap semiconductors sic gan and diamond
Advantages of wide bandgap semiconductors(SiC, GaN and diamond)
  • 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 oC due to the high intrinsic temperature
    • Low noise
advantages
Advantages
  • 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

Fmax : 50 GHz

advantages1
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)
  • High Saturated velocity
    • SiC 2.2 x107 m/s

2 times higher than that of Si and GaAs

    • Si and GaAs: 1 x107 m/s
slide32
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
growth of sic single crystal
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
physical vapor transport pvt growth of sic single crystal wafers
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: 2000-2300oC
    • DT of 10-30C controlled by moving RF coil
    • Growth rate controlled by DT and pressure in reactor
defects in sic wafer
Defects in SiC wafer
  • Micropipes– breakdown at low voltage
  • Dislocations
  • Low angle grain boundaries
  • Stacking faults
gmu wbgs research projects ion implantation of sic wafers
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.
rapid annealing of ion implanted sic
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; 200oC/min, total time: 20 min.
    • Conventional: heating rate: 10oC/min, total time 3 hr.
  • Rutherford backscattering (RBS) measurements are conducted before and after ion-implantation to study the recovery of the crystal lattice.
slide44

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.

best reported sheet resistivity of ion implanted sic
Best Reported Sheet Resistivity of Ion Implanted SiC

. Figure 2. Sheet resistivity of Al implants into 6H silicon carbide at room tmperature

Figure 1. Sheet resistivity of nitrogen implants into 6H silicon carbide at room tmperature

slide46
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
sic microwave power devices
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%
high power 4h sic static induction transistors sits
High power 4H-SiC static induction transistors (SITs)

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).

Measured static I-V characteristics of a SIT

slide49
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..

high power sic mesfet
High power SiC MESFET
  • Three epitaxial layers
    • P buffer layer
    • Channel layer doped Nd=3x1017cm-3
    • Heavily doped n+ cap layer
  • Performance
    • Pmax : 15W
    • Frequency: 2.1 Ghz
    • Power density: 1w/mm
    • PAE; 54%

a

slide52

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

slide54
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
gan power high electronic mobility transistors
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 cm2/Vs
  • High frequency 100GHz
  • High power density: 10w/mm
  • Base station microwave power amplifier
  • highly linear mixers
  • high power switches