肖特基二极管的特性和可靠性测试
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• Commercial diodes (GaAs foundry)
– Design limitations
• Europe
– Darmstadt, Germany – Cork, Ireland – Bath, UK
UMS Schottky diode
• Not a current source for production of diodes that are sensitive to the needs of the European community • RAL is hoping to fill this gap, however, work needs to be done to optimise the fabrication process and test their reliability – This is the motivation for this project
Characterising and Reliability testing of
How do they work?
• In equilibrium • No来自百度文库 in contact
Characterising and Reliability testing of
How do they work?
– Combines two input signals and output the difference – Mixing does not change the spectral shape or bandwidth – Schottky diodes do not require cooling
Characterising and Reliability testing of
What frequency can they work to? • Any frequency…however power becomes a problem!! • Figure of merit is used:
Can Schottky diodes be used as HG?
OUTPUT DIODE
INPUT
Characterising and Reliability testing of
Can Schottky Diodes be used for anything else?
• Mixing devices
• Causes of deviation:
– Surface imperfections – Quantum tunnelling – Edge effects
Characterising and Reliability testing of
How can you tell if they’re good?
0.60
0.65 Voltage [V]
0.70
0.75
Characterising and Reliability testing of
How can you tell if they’re good?
Calculated Resistance as a Function of Measurement Current
Simplified mixing circuit
Characterising and Reliability testing of
What do they look like?
40 µm 20 µm 20 µm
Anti parallel
•Two anodes •Mixers
120 4 µm µm
• • • • • THz technology How Schottky diodes work Diode development Evaluate the effects of measuring and impact heating Further work and conclusion
The spectral region between ~100 GHz and 3 THz is still largely unexplored, with wide ranging and cross disciplinary applications
Where is the main capacitance?
Side view
Birds eye view
Characterising and Reliability testing of
Outline
• • • • • THz technology How Schottky diodes work Diode development Evaluate the effects of measuring and impact heating Further work and conclusion
Characterising and Reliability testing of
Why is there a gap?
There are no devices capable of generating significant power at these frequencies!!!
100
CW output power [Watt]
10 1 100 m
Electronic IMPATT THz gap RTD RTD array .1 1
Optical
QC Laser
10 m TUNNETT 1m 100 µ 10 µ 1µ .01 Gunn
HG
10
100
Frequency [THz]
Characterising and Reliability testing of
Characterising and Reliability testing of
Outline
• • • • • THz technology How Schottky diodes work Diode development Evaluate the effects of measuring and impact heating Further work and conclusion
Characterising and Reliability Testing of THz Schottky Diodes Chris Price
Supervisor: Dr Byron Alderman
Characterising and Reliability testing of
Outline
• Series resistance (Rs)
• Rs~10–15O
∆Vd Rs = Id
• Causes
– Highly doped areas in semi conducting material – Size of anode
Characterising and Reliability testing of
How can you tell if they’re good?
Measured I – V compared to ideal I – V of a diode
1.E-03
? Vd
1.E-04 Current [A] 1.E-05
MEASURED DIODE IDEAL DIODE
1.E-06 0.55
qV nF − nZ = nd (exp( ) − 1) k BT
qV I (V ) = I 0 (exp( ) − 1) kBT
I 0 = A **T 2W exp( − qφ b ) kBT
Diode I – V equation Reverse saturation current (constant of proportionality)
Characterising and Reliability testing of
How can you tell if they’re good? • Ideality factor (?)
• ?~1.1-1.2
qV I (V ) = I 0 (exp( ) − 1) ηk B T
η= q ∆V log(e) k BT
– No influence over design – Concern over future availability
VDI Schottky diode
Characterising and Reliability testing of
Where can I get one - Non-USA?
Single anode
•One anode •Multipliers
Planar Schottky diode
Characterising and Reliability testing of
What do they look like?
Air Bridge
Schottky Contact
Ohmic
Characterising and Reliability testing of
How can I make one?
Animation of fabrication process •Photoresist (brown) •Masks •Chemicals •Evaporators •Time
Depletion zone
In equilibrium and in contact (zero bias)
1. 2. 3. The Fermi level through the system must be constant if it is in equilibrium The electron affinity must be constant The free space energy level must be continuous
20
16 Spreading Resistance [ohms]
RAL
12
8
VDI
4
0 0 5 10 15 Current [mA] 20 25 30
Characterising and Reliability testing of
How do you calculate the ideality and series resistance? • Standard parameters
−E n1 = nd exp( ) k BT
• Where E = -q(f -V) & n is the doping density
bi
d
Characterising and Reliability testing of
Some maths…
Difference in charge density states for forward and zero bias conditions
1 fc = 2πRs C j 0
• At high frequencies skin effects in the anode cause resistance to increase therefore reducing performance
Characterising and Reliability testing of
Characterising and Reliability testing of
How do they work?
No longer in equilibrium
Current
Characterising and Reliability testing of
Some maths…
• Current flows by primarily by Thermionic Emission • I a (nf – nz) • Current density is given by Maxwell – Boltzmann distribution
Characterising and Reliability testing of
Where can I get one – USA?
• Jet Propulsion Laboratory, JPL
– Only for specific NASA programs
• University of Virginia (Virginia Diodes Inc.)
– Design limitations
• Europe
– Darmstadt, Germany – Cork, Ireland – Bath, UK
UMS Schottky diode
• Not a current source for production of diodes that are sensitive to the needs of the European community • RAL is hoping to fill this gap, however, work needs to be done to optimise the fabrication process and test their reliability – This is the motivation for this project
Characterising and Reliability testing of
How do they work?
• In equilibrium • No来自百度文库 in contact
Characterising and Reliability testing of
How do they work?
– Combines two input signals and output the difference – Mixing does not change the spectral shape or bandwidth – Schottky diodes do not require cooling
Characterising and Reliability testing of
What frequency can they work to? • Any frequency…however power becomes a problem!! • Figure of merit is used:
Can Schottky diodes be used as HG?
OUTPUT DIODE
INPUT
Characterising and Reliability testing of
Can Schottky Diodes be used for anything else?
• Mixing devices
• Causes of deviation:
– Surface imperfections – Quantum tunnelling – Edge effects
Characterising and Reliability testing of
How can you tell if they’re good?
0.60
0.65 Voltage [V]
0.70
0.75
Characterising and Reliability testing of
How can you tell if they’re good?
Calculated Resistance as a Function of Measurement Current
Simplified mixing circuit
Characterising and Reliability testing of
What do they look like?
40 µm 20 µm 20 µm
Anti parallel
•Two anodes •Mixers
120 4 µm µm
• • • • • THz technology How Schottky diodes work Diode development Evaluate the effects of measuring and impact heating Further work and conclusion
The spectral region between ~100 GHz and 3 THz is still largely unexplored, with wide ranging and cross disciplinary applications
Where is the main capacitance?
Side view
Birds eye view
Characterising and Reliability testing of
Outline
• • • • • THz technology How Schottky diodes work Diode development Evaluate the effects of measuring and impact heating Further work and conclusion
Characterising and Reliability testing of
Why is there a gap?
There are no devices capable of generating significant power at these frequencies!!!
100
CW output power [Watt]
10 1 100 m
Electronic IMPATT THz gap RTD RTD array .1 1
Optical
QC Laser
10 m TUNNETT 1m 100 µ 10 µ 1µ .01 Gunn
HG
10
100
Frequency [THz]
Characterising and Reliability testing of
Characterising and Reliability testing of
Outline
• • • • • THz technology How Schottky diodes work Diode development Evaluate the effects of measuring and impact heating Further work and conclusion
Characterising and Reliability Testing of THz Schottky Diodes Chris Price
Supervisor: Dr Byron Alderman
Characterising and Reliability testing of
Outline
• Series resistance (Rs)
• Rs~10–15O
∆Vd Rs = Id
• Causes
– Highly doped areas in semi conducting material – Size of anode
Characterising and Reliability testing of
How can you tell if they’re good?
Measured I – V compared to ideal I – V of a diode
1.E-03
? Vd
1.E-04 Current [A] 1.E-05
MEASURED DIODE IDEAL DIODE
1.E-06 0.55
qV nF − nZ = nd (exp( ) − 1) k BT
qV I (V ) = I 0 (exp( ) − 1) kBT
I 0 = A **T 2W exp( − qφ b ) kBT
Diode I – V equation Reverse saturation current (constant of proportionality)
Characterising and Reliability testing of
How can you tell if they’re good? • Ideality factor (?)
• ?~1.1-1.2
qV I (V ) = I 0 (exp( ) − 1) ηk B T
η= q ∆V log(e) k BT
– No influence over design – Concern over future availability
VDI Schottky diode
Characterising and Reliability testing of
Where can I get one - Non-USA?
Single anode
•One anode •Multipliers
Planar Schottky diode
Characterising and Reliability testing of
What do they look like?
Air Bridge
Schottky Contact
Ohmic
Characterising and Reliability testing of
How can I make one?
Animation of fabrication process •Photoresist (brown) •Masks •Chemicals •Evaporators •Time
Depletion zone
In equilibrium and in contact (zero bias)
1. 2. 3. The Fermi level through the system must be constant if it is in equilibrium The electron affinity must be constant The free space energy level must be continuous
20
16 Spreading Resistance [ohms]
RAL
12
8
VDI
4
0 0 5 10 15 Current [mA] 20 25 30
Characterising and Reliability testing of
How do you calculate the ideality and series resistance? • Standard parameters
−E n1 = nd exp( ) k BT
• Where E = -q(f -V) & n is the doping density
bi
d
Characterising and Reliability testing of
Some maths…
Difference in charge density states for forward and zero bias conditions
1 fc = 2πRs C j 0
• At high frequencies skin effects in the anode cause resistance to increase therefore reducing performance
Characterising and Reliability testing of
Characterising and Reliability testing of
How do they work?
No longer in equilibrium
Current
Characterising and Reliability testing of
Some maths…
• Current flows by primarily by Thermionic Emission • I a (nf – nz) • Current density is given by Maxwell – Boltzmann distribution
Characterising and Reliability testing of
Where can I get one – USA?
• Jet Propulsion Laboratory, JPL
– Only for specific NASA programs
• University of Virginia (Virginia Diodes Inc.)