DHBT With Esaki Base Emitter Junction having a 60 nm Wide Emitter Contact

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DHBT With Esaki Base Emitter Junction having a 60
nm Wide Emitter Contact

• 20th IPRM, 25-29 MAY 2008, Versallies-France
• D. Cohen Elias, A. Gavrilov, S. Cohen, S. Kraus,
  and D. Ritter
• Department of Electrical Engineering, Technion
  Israel Institute of Technology
• Haifa, Israel

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HBT Scaling Law
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DHBT WITH ESAKI BASE EMITTER JUNCTION
300nm
60nm
B
E
Ielectrons
Iholes
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Advantages

• Base contact to p-type material eliminated.
• Emitter and base contacts can be fabricated
  simultaneously by in situ methods to obtain
  reproducibly low contact resistance (E. Lind et
  al. DRC 2007).

Limitations

• Backward diode resistivity.
• Transistor must operate at higher current density
  than the Esaki tunneling valley current density.
• Non self aligned base metal deposition.
  (Cbc1.5Cbc,scaling)
• Possibly larger Cbe.

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Backward diode resistivity
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Low Vpeak is essential !
Vpeak(EF,nEF,p)/3
EF,p
EF,n
Fermi level position in n-type GaInAs determined
by the Burstein- Moss shift, Martin Munoz et al.,
Physical Review B, Vol 63 , 2001
T.A Demassa et al.Solid-State Electron., Vol
13,1970
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Cbe of Esaki junction versus conventional
junction
nJe/q?e gt ND Cbee/LDebye LDebye10-20 nm
Conventional heterojunction
InP
InGaAS
B. Sheinman and D. Ritter. TED 2003
EF,n
Cbee/L depletion nJe/q?e lt ND
InGaAS
InP
Esaki heterojunction
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Previous related work the multi emitter approach
for logic applications
K. Imamura et al., Electronics Lett. Vol. 30 No.
5, 1994 A. Zaslavsky et al., EDL Vol. 18, No. 9,
1997
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Layer Structure

D. Cohen Elias et al. EDL, vol. 26, 2005
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SIMS Profile
Emitter cap
Emitter
Base
Collector
Concentration (cm-3)
Si Pulse
Si C
Depth (nm)
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Fabrication using 3 e-beam lithography and 2
photolithography steps
Emitter Base metal evaporation
Base mesa formation
300nm
60nm
B
E
Isolation
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Gummel Plot and Common Emitter
Ae0.06X0.6 µm2 Ib,step5µA
dJKirk/dVce,
M. Rodwell Short Course IPRM 2005
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Gummel Plot and Voltage Controlled Common Emitter

Ae0.06X0.6 µm2 , Vb,step50mV
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Estimation of the backward diode resistivity
Ae 160X1600 nm2
Ae60X600 nm2
1.5 Vpeak
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Higher emitter doping is possible
Si 21020(cm-3)
Concentration (cm-3)
Si C
Depth (nm)
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Conclusions

• DHBT with Esaki base emitter junction
  (NDE11020cm-3) having 60 nm wide emitter
  contact was fabricated.
• The Esaki tunneling current did not degrade the
  gain of the device at high current density.
• Low Vpeak values were found.
• Esaki peak current density should be increased
  from 1(mA/µm2) to about 50-100(mA/µm2) to achieve
  the scaling roadmap base contact resistance

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• Thank You