1. An X-Band Low Noise InP-HBT VCO
with Separate Optimized Varactor Layers
T. Magrisso (1)
D. Elad (1)
N. Buadana (1)
S. Kraus (2)
D. Cohen Elias (2)
A. Gavrilov (2)
S. Cohen (2)
D. Ritter (2)
(1) RAFAEL, Armament Development Authority Ltd., Microelectronic Directorate
(2) Department of Electrical Engineering, Technion-Israel Institute of Technology

2. InP Based VCOs Record frequencies
Optoelectronic integration: Optoelectronic Oscillitor,
Clock recovery, etc..

3. Previous work on InP HBT circuits at Technion:
43 GHz integrated
TWA photoreceiver
75 GHz TWA

4. Varactors in InP HBT VCOs
Previous InP HBT VCOs used base collector layers
as varactor layers.
Optimized HBT requires fully depleted collector
at Vbc=0, for minimum VCO’s phase noise.
As a results, small tuning range is obtained

5. Conventional InP HBT technology
10um
1um P N N+
InP N Emitter N P
Ga InAs P Base N
Ga InAs N Collector N+
Ga InAs N Sub-Collector
InP Semi-insulating Substrate

6. Separate varactor layers
Varactors and HBTs can be separately optimized.
Varactor layers can be grown either above or underneath
the transistor layers.
Varactor layers underneath transistor layers
complicate interconnect.
Varactor layers above transistor layers
require stepper technology.

7. InP HBT technology with Separate Varactor Layers
InP N Emitter N
Ga InAs P Base
InP N Collector N+
InP N Sub-Collector P N
Ga InAs P Base
InP N Varactor N N+
InP N Varactor Connect
InP Semi-insulating Substrate

8. This Work Carried out by contact lithography-varactor layers
underneath transistor layers.
Wide tuning range Colpitts X band VCO demonstrated
as first attempt.
Simplified VBIC transistor model predicts well
VCO’s performance.

9. Transistor Properties
Ft=180 GHz
Fmax=200GHz
Vturn-on=0.5V
Vce-breakdown=5V
Ic max (Vce=3v)=30mA
βAC=50

10. Transistor Modeling DC Measurements and s-parameters
Small-signal equivalent circuit parameters extraction.
Degenerate VBIC model with 18 parameters only

11. VBIC large signal model

12. VBIC model parameters extracted at specific bias,
Does it work for large signal VCO modeling ?

13. Varactor Design & Modeling
We have compared 2 types of varactors:
Base-Collector layers.
Separate layers with Nd=1017 cm-3.

14. Varactor Modeling
Different size varactors, for scaleable model extraction.
Semi-lumped model
Rectangular varactors achieving 1 ohm series resistance.

15. Varactor modeling
Using simple model with text book equations.

16. VCO schematics – Colpitts configuration

17. Full EM Simulation

18. Testing VCO

19. Comparison between Measurement and
Simulation with degenerate VBIC model

20. Measured phase noise

21. Phase Noise Simulation
Phase noise parameters extraction for VBIC model
Kfn=1E-12
Afn=1

22. Conclusions InP HBT X band VCO with separate varactor layers
underneath transistor layers achieved tuning range of
12% and phase noise of -94dB/Hz at 100KHz.
Future work: VCO layers on top of transistor layers for
higher frequencies, and optoelectronic applications. .

23. Acknowledgement We would like to thank …..
Dr. David Rosenfeld for supporting the project.
Rafael Microelectronic Direcrotate Design groupe
and Testing House.
Technion Russell Berrie Nanotechnology Institute.
Liron Arazi and Kochavi Shemuel for design and
testing assistance.
Dr. Asher Madjar.