Single Event Transient Response of InGaAs MOSFET Kai Ni 1 , En Xia - - PowerPoint PPT Presentation

Single Event Transient Response of InGaAs MOSFET

Kai Ni1, En Xia Zhang1, Nicholas C. Hooten1, William G. Bennett1, Michael W. McCurdy1, Ronald D. Schrimpf1, Robert A. Reed1, Daniel M. Fleetwood1, Michael L. Alles1, Tae-Woo Kim2, Jianqiang Lin3, Jesús A. del Alamo3

1Vanderbilt University, Nashville, TN 37235, USA 2SEMATECH 3Massachusetts Institute of Technology, Cambridge, MA 02139 USA 6/23/14 RER group meeting 1

Motivation

• III-V materials are promising channel candidates at beyond

14nm technology node

• Previous transient studies focus on III-V MESFET/HEMT
• Gate transients
• Charge enhancement due to source drain pathway
• Gate bias dependence shows a peak at threshold voltage
• It’s important to study the transient response of III-V MOSFET

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Device II

• Cross section and vertical band diagram

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0.00 0.02 0.04 0.06 0.08

• 4
• 3
• 2
• 1

1 2

energy (eV) position (µm) Conduction Band Fermi Level Valance Band

Heavy Ion Results

• No gate transient due to large barrier
• Source and drain transient have the same magnitude
• Two processes with different time constant

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• Fast collection: τ≈ 100 ps, direct

collection

• Slow collection: τ≈ 3 ns, source-to-

drain pathway

10 20 30 40 50

• 0.3
• 0.2
• 0.1

0.0 0.1 0.2 0.3

current (mA) time (ns) drain source gate

Gate Bias Dependence

• Peak drain current reaches a maximum around threshold voltage
• Peak drain current decreases considerably in inversion and slightly in

depletion and accumulation

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• 0.8
• 0.6
• 0.4
• 0.2

0.0 0.2 0.4 0.6 0.24 0.26 0.28 0.30 0.32 0.34 0.36

peak drain current (mA) VGS-VTH (V)

Laser Irradiation

• Laser wavelength 1.26 μm
• Photon energy 0.98 eV, larger than the channel material

bandgap, smaller than the other matherials

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XX’ 40 µm 10 µm

4 µm

Laser Results

• Line scan
• The drain side strike has a larger peak drain current than the source side

strike

• The drain side has a higher electric field than the source side (VDS=0.5 V), so

the electron velocity is higher in drain side, the peak drain current is larger

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• 2
• 1

1 2 2.0 2.1 2.2 2.3 2.4 2.5

Drain peak drain current (mA) x position (µm) Source

Gate Bias Dependence

• The laser data is consistent with heavy ion data
• The peak drain current is maximum around threshold and decreases

considerably in inversion while slightly in depletion and accumulation

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• 0.8
• 0.6
• 0.4
• 0.2

0.0 0.2 0.4 0.6 1.7 1.8 1.9 2.0 2.1 2.2 2.3 2.4 2.5

peak drain current (mA) VGS-VTH (V)

2D TCAD Simulation

• Model
• The LET is 0.1 pC/μm
• The ion strike is gaussian both in space and time
• The strike center is at 0.2 μm and 1.0 ns

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0.2 0.4

• 0.2
• 0.4

0.2 InAlAs

InGaAs

InGaAs InGaAs HfO2 X X’ Y’ Y source drain gate

X (µm) Y (µm)

2D TCAD Simulation

• Hole density (colored map) and electrical potential (contour)
• At the center of the strike, the electric potential is strongly distorted due to

a large number of electrons and holes are generated around the strike location

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Pre Strike Hole Density 0.1 0.2 0.3

• 0.1
• 0.2

0.1 0.2 0.3

• 0.1
• 0.2

0.1 0.2 0.3

• 0.1
• 0.2

0.1 0.2 0.3

• 0.1
• 0.2

1.0 ns

2D TCAD Simulation

• Hole density (colored map) and electrical potential (contour)
• At 1.2 ns, the electric potential in the buffer recovers. Electrons and holes

move to the channel layer. Only the channel layer is strongly perturbed

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0.1 0.2 0.3

• 0.1
• 0.2

0.1 0.2 0.3

• 0.1
• 0.2

1.0 ns

0.1 0.2 0.3

• 0.1
• 0.2

0.1 0.2 0.3

• 0.1
• 0.2

1.2 ns

X (µm) Y (µm)

2D TCAD Simulation

• Conduction band along the horizontal cut and vertical cut
• Electric field exists before strike to stop holes entering channel, but it is almost zero after
• strike. Electrons and holes flood into the channel
• Electric potential is distorted around the strike location at the center of strike (1.0 ns) but

recovers quickly

• At pre-strike, the source-channel barrier is 0.52 eV, but reduces to 0.03 eV at 1.2 ns. The

device is ON

• The source-channel barrier is slowly recovered, which lasts for a few nanoseconds

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• 0.6
• 0.4
• 0.2

0.0 0.2 0.4 0.6

• 1.0
• 0.8
• 0.6
• 0.4
• 0.2

0.0 0.2 0.4

conduction band (eV) x position (µm) 1.0 ps 1.0 ns 1.2 ns 1.6 ns 2.1 ns 6.0 ns 10.0 ns

• 0.01

0.00 0.01 0.02 0.03 0.04

• 0.5

0.0 0.5 1.0 1.5 2.0 2.5 3.0

1.0 ps 1.0 ns 1.2 ns 1.6 ns 2.1 ns 6.0 ns 10.0 ns conduction band (eV) y position (µm)

2D TCAD Simulation

• Conduction band and excess electron density at different gate biases
• The voltage drop along the channel region decreases with gate bias, leading to

smaller horizontal electric field, hence smaller velocity

• The absolute excess electron density, the difference between post-strike and pre-

strike electron density, reaches a maximum around threshold, decreases considerably in inversion and slightly in depletion and accumulation

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• 0.4
• 0.2

0.0 0.2 0.4

• 0.80
• 0.75
• 0.70
• 0.65
• 0.60
• 0.55
• 0.50
• 0.45
• 0.40

conduction band energy (eV) x position (µm) VGS=-0.4 V VGS=-0.2 V VGS= 0.2 V VGS= 0.4 V

0.000 0.002 0.004 0.006 0.008 1x10

18

2x10

18

3x10

18

4x10

18

5x10

18

6x10

18

7x10

18

8x10

18

9x10

18

excess electron density (cm

• 3)

y position (µm) VGS=-0.4 V VGS=-0.2 V VGS= 0.2 V VGS= 0.4 V

Comparison

• Comparison of the gate bias dependence between heavy ion, laser and

2D TCAD simulation

• The heavy ion data, the laser data and 2D TCAD simulation data agree

very well

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• 0.8
• 0.6
• 0.4
• 0.2

0.0 0.2 0.4 0.6 0.60 0.65 0.70 0.75 0.80 0.85 0.90 0.95 1.00 1.05

Laser Results Heavy Ion Results 2D TCAD Simulation normalized peak current VGS-VTH (V)

Conclusion

 No gate transients due to large barrier for both electron and hole between gate dielectric and semiconductor  The slow holes piling up under the gate and the source access region modulates the source channel barrier, turning ON the device and enhancing the collected charge  The peak drain current is maximum for gate biases around threshold and decreases considerably in inversion and slightly in depletion and accumulation  Depending on the application and the opportunities for remediation, these transient responses may impose limitations on the use of some types of alternative-channel materials in space applicaiton

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