1. DHBT With Esaki Base Emitter Junction having a 60 nm Wide Emitter Contact
20th IPRM, 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

2. HBT Scaling Law
M. Rodwell et al, IEEE BCTM (2007)

3. DHBT WITH ESAKI BASE EMITTER JUNCTION
300nm
60nm B E
Ielectrons
Iholes

4. Advantages Limitations 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. (Cbc~1.5Cbc,scaling)
Possibly larger Cbe.

5. Backward diode resistivityJ
VBE
VPeak
JPeak
JValley

6. Low Vpeak is essential ! Vpeak=(EF,n+EF,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

7. Cbe of Esaki junction versus conventional junction
n=Je/qυe > ND
Cbe~ε/LDebye
LDebye~10-20 nm
Conventional heterojunction
InP
InGaAS
B. Sheinman and D. Ritter. TED 2003
EF,n
Cbe~ε/L depletion
n=Je/qυe < ND
InGaAS
InP
Esaki heterojunction

8. 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

9. Layer Structure *
* D. Cohen Elias et al. EDL, vol. 26, 2005

10. SIMS Profile Emitter cap Emitter Base Collector Concentration (cm-3)
Si Pulse Si C
Depth (nm)

11. Fabrication using 3 e-beam lithography and 2 photolithography steps
Emitter & Base metal evaporation
Base mesa formation
300nm
60nm B E
Isolation

12. Gummel Plot and Common Emitter
Ae=0.06X0.6 μm2
Ib,step=5μA
dJKirk/dVce, *
* M. Rodwell Short Course IPRM 2005

13. Gummel Plot and Voltage Controlled Common Emitter
Ae=0.06X0.6 μm2 , Vb,step=50mV

14. Estimation of the backward diode resistivity
Ae= 160X1600 nm2
Ae=60X600 nm2
1.5 Vpeak

15. Higher emitter doping is possible
Si: 2∙1020(cm-3)
Concentration (cm-3) Si C
Depth (nm)

16. Conclusions
DHBT with Esaki base emitter junction (NDE=1∙1020cm-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 (mA/μm2) to achieve the scaling roadmap base contact resistance

17. Thank You