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Superconducting Integrated Receiver Based on Nb-AlN-NbN-Nb Circuits
Mikhail Torgashin, Valery Koshelets, Pavel Dmitriev, Andrey Ermakov, Lyudmila Filippenko
Institute of Radio Engineering and Electronics (IREE), Moscow, Russia

and Pavel Yagoubov
SRON Netherlands Institute for Space Research, the Netherlands

August 30, 2006

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Superconducting Integrated Receiver Based on Nb-AlN-NbN-Nb Circuits
The Superconducting Integrated Receiver (SIR) comprising in one chip a superconductor-insulator-superconductor (SIS) mixer and a phaselocked superconducting Flux Flow Oscillator (FFO) is under development for the international project TELIS. To overcome temperature constraints and extend operation frequency of the SIR we have developed and studied Nb-AlN-NbN-Nb circuits with a gap voltage Vg up to 3.7 mV and extremely low leakage currents (Rj/Rn > 30). Based on these junctions integrated microcircuits comprising FFO and harmonic mixer have been designed, fabricated and tested; the radiation from such circuits has been measured at frequencies up to 700 GHz. Employment of NbN electrode does not result in the appearance of additional noise. For example, FFO linewidth as low as 1 MHz was measured at 600 GHz, that allows us to phase lock up to 87 % of the emitted by FFO power and realize very low phase noise about ­ 90 dBc. Preliminary results demonstrated uncorrected DSB noise temperature of the Nb-AlN-NbN SIR below 250 K at frequencies around 600 GHz
August 30, 2006 ASC-2006 Seattle Nb-AlN-NbN SIR 3EG08 2


TELIS - TErahertz LImb Sounder
TELIS Objectives: Measure many species for atmospheric science (ClO, BrO, O3, HCl, HOCl, etc); - Chemistry, Transport, Climate Serve as a test platform for new sensors Serve as validation tool for future satellite missions Three independent frequency channels, cryogenic heterodyne receivers:
500 GHz by RAL 600-650 GHz by SRON-IREE 1.8 THz by DLR (PI)
August 30, 2006 ASC-2006 Seattle Nb-AlN-NbN SIR 3EG08 3


Schematics of PLL SIR
4 K dewar

SIR chip
SIS mixer
Harmonic mixer
FFO as LO 550-650 GHz

HEM T 4-8 G H z

IF Processor & DAC

20 GHz reference

C om puter controlled data acquisition sy stem
Electronics FFO , SIS, H M control

HEM T
4 GHz

PLL
August 30, 2006

LSU

400 M H z reference
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Photo of the T4m SIR chip

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SIR Microcircuit for TELIS

Double-slot twin SIS ­ 0.8 µm

2

FFO 400*16 µm

2

HM ­ 1.0 µm

2

4 x 4 x 0.5 mm3 (Si);

Nb-AlOx-Nb; Jc = 5 - 8 kA/cm

2 2

Optionally: SIS ­ Jc = 8 kA/cm2; FFO + HM = 4 kA/cm
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IVCs of the Nb-AlOx-Nb FFO measured at different CL currents (red = > 25% of SIS Ig)

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The electrical scheme of the nitridation process

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The dependency of Rj/Rn ratio on critical current densities for different types of junctions
Rn*S, *µ
200 40 35 30 25 Rj/Rn 20 15 10 5 0 1 10 Jc, kA/cm
August 30, 2006
2

2

20

2

Nb-AlOx-Nb Nb-AlN-Nb Nb-AlN-NbN

100

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IV characteristic of Nb-AlN-NbN junction S= 2 µm2, RnS = 37 µm2, Jc= 6.5 kA/cm2, Ic = 0
T3-061#01 (Vg=3.67 mV, Rn=19Ohm, Rj/Rn=33)
300 250
SIS Current (mkA)

200 150 100 50 0

0

1

2

3

4

5

6

SIS Voltage (mkA)
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IVCs of the Nb-AlN-NbN-Nb FFO measured at different magnetic fields

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Nb-AlN-NbN SIR ­ new features

Wednesday, August 30, 2:00pm - 4:00pm; Report 3EG08
August 30, 2006 ASC-2006 Seattle Nb-AlN-NbN SIR 3EG08 12


Maximum current detected by HM at V = 2.5 mV normalized on the current rise at Vg
Normalized SIS Pumping Level (a.u.)
1

N b /AlN /N b N N b /AlO x /N b

0.1
0 100 200 300 400 500 600 700 800 900

FFO Fr e q ue nc y ( G Hz )
August 30, 2006 ASC-2006 Seattle Nb-AlN-NbN SIR 3EG08 13


IVC of an SIS mixer pumped by FFO
H D 13-09#26 (V g =3.7m V)
300

250

SIS Current (mkA)

200

150

100

50

FF O F requenc y: 0 GHz 400 G H z 500 G H z 600 G H z 700 G H z
0 1 2 3 4 5 6 7

0

SIS Voltag e (m V)
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A set of SIS IV-curves, pumped by FFO at 500 GHz

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SIS mixer pumping at different Nb-AlN-NbN FFO bias (output power) setting

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A close-up of FFO IVC in Fiske steps region

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Nb-AlN-NbN circuits: LW on frequency
20
Nb Nb Nb Nb N, Ib=47mA N, Various Ib , Ib=30mA , Ib=42mA

15 Linewidth (MHz)

10

5

0 350

400

450

500

550

600

650

700

750

FFO Frequency (GHz)
Wednesday, August 30, 2:00pm - 4:00pm; Report 3EG08
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Down-converted spectra of the FFO operating at 671 GHz
0

-10

Frequency-Locked FFO Phase-Locked FFO Resolution Banwidth RBW = 1 MHz

FFO Power (dBm)

-20

-30

-40

-50 340

360

380

400

420

440

460

Down-converted FFO Frequency (MHz)
August 30, 2006 ASC-2006 Seattle Nb-AlN-NbN SIR 3EG08 19


Down-converted spectra of the FFO operating at 671 GHz. Span ­ 100 Hz.
0

-20

Spectrum analyzer Resolution Banwidth RBW = 1 Hz

Power (dBm)

-40

-60

-80

-100 -50

-40

-30

-20

-10

0

10

20

30

40

50

Offset from carrier (Hz)
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Nb-AlN-NbN SIR: Tn on FFO frequency
2000 1800
T 3-061#01 T 3-071#01

Noise Temperature (K)

1600 1400 1200 1000 800 600 400 200 0 450 500 550 600

650

700

Receiver Frequency (GHz)
Wednesday, August 30, 2:00pm - 4:00pm; Report 3EG08
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Nb-AlN-NbN-Nb SIR: Noise temperature on SIS bias voltage
1000 900

Noise Temperature (K)

800 700 600 500 400 300 200 100 0 1.5 2.0 2.5

T3-061#01

3.0

3.5

SIS Voltage (mV)
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Beam pattern of Nb-AlN-NbN-Nb SIR

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