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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Traveling wave tube
Single mode cavity for Microwave sintering of advanced ceramics
200w aperture HID lamps (7mm) driven by solid state microwave devices
1400wmagnetron driven HID lamps,
Pmax a Vmax x Imax
PD = Vmax x Current density
f maxa (Vs/L)
Depends on wave shape, impedance, leakage current and power gain
< 5 GHz
100-600W at 1 GHz
> 40% Efficiency
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: 40VWidely used Si microwave devices
Frequency band Power (W) cost ($)
C and S 10 300 20 600 30 900
Ku 10 1000 15 1500
HEMT (High electronic mobility transistor)
HBT (heterojunction bipolar junction transistor)
3 times higher than that of Si and GaAs
Fmax : 50 GHz
3. High thermal conductivity
10 times higher than that of Si and GaAs
2 times higher than that of Si and GaAs
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.
. 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
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
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..
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