Atacama Large Millimeter/submillimeter ArrayExpanded Very Large Array

Robert C. Byrd Green Bank TelescopeVery Long Baseline Array

NRAO Millimeter/THz Development Program: Current and Future

ALMA Development

• ALMA Development Workshop (March 21-22)• Band 3 (or Band 2/3) MMIC LNA Upgrade• Band 6 Balanced Mixer Upgrade• SIS Mixer Development for Band 10 and beyond• Focal Plane Arrays

2Millimeter/THz Development at the NRAO CDL

Band 3 (or 2/3) LNA Upgrade

• Using 35nm InP HEMT MMIC LNA• 67-90 GHz 1st iteration (EBLNA81)• New designs funded by KISS (Keck Institute for Space

Studies): EBLNA81B, EBLNAW+, EBLNAW0, MMLN100– Fabrication complete, diced chips expected in ~2 weeks

• ~25% Sensitivity Improvement for Band 3• M. Morgan has designed a MMIC Schottky “SIS-substitute”

mixer• Directly applicable to GBT 3mm FPA• Could also be used as W-band IF LNA for SIS or Schottky

mixer

3Millimeter/THz Development at the NRAO CDL

EBLNA81B: Retuned for 67-90 GHz35nm 3-stage LNA (EBLNA81)

(Vd1=0.5V,Vd2=0.8V,Vd3=0.8V)(Id1=1.5mA,Id2=3.0mA,Id3=3.0mA)

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WR-12 mixerWR-10 mixerSim:EBLNA81Sim: EBLNA81B

C:\Documents and Settings\ebryerto\My Documents\eblna81_cold11.xls

L13: 65 to 34umL14: 78 to 144um L14

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Millimeter/THz Development at the NRAO CDL

EBLNAW+: Cover full 68-116 GHz band

5Millimeter/THz Development at the NRAO CDL

MMLN100: Cover full 68-116 GHz band

6Millimeter/THz Development at the NRAO CDL

EBLNAW0: A “Tunable” MMIC LNA

7Millimeter/THz Development at the NRAO CDL

UVML/NRAO/UAz SIS Collaboration• 5 year program funded by ALMA Operations, beginning

FY09• Advanced Materials and Processing Techniques

– AlN Barriers for Wide Bandwidth (and NbTiN)– Nb/AlN/NbTiN SIS Junction Development (up to ~1.2 THz)

• Superconducting Hybrid Development (UAz funded)• 0.7mm and 0.35mm Balanced/Sideband-Separating Mixers• >1THz SIS Mixers (for SOFIA, ALMA Band 11, etc.)• Balanced SIS Mixer for Band 6 (IF bandwidth to 4-12 GHz)

8Millimeter/THz Development at the NRAO CDL

SIS Materials and Processing Development• Nb/AlN/NbTiN SIS mixers with AlN barriers are expected to

yield near quantum-limited noise up to 1.2 THz• Characterization of NbTiN film properties at 4K

– Used cryogenic probe station to measure capacitance and penetration depth (surface inductance)

– Will improve accuracy of mixer designs• Delivery of hot deposition system in Jan. 2010

– Single crystal Nb tuning circuits– NbTiN with higher Tc– New materials…

9Millimeter/THz Development at the NRAO CDL

Silicon Membrane Beamlead Circuits

Millimeter/THz Development at the NRAO CDL 10

• 3mm thick Silicon substrate• Can be cut to arbitrary shape• Can be patterned with Nb or NbTiN• Beamleads allow for easy and repeatable assembly• Used in current design of 700mm SIS mixer chips and

superconducting 3dB hybrid chips

Drop-In Superconducting Hybrids

• For easy design and assembly of balanced and sideband-separating mixer modules

• 375-500 GHz (WR-2.1) prototype• Works as expected at room temperature, currently being

measured cold• UVML funding partly from UAz

11Millimeter/THz Development at the NRAO CDL

287 mm

Balanced SIS Mixers• Rejection of LO noise• 50-100 times less LO power• 3dB greater dynamic range• Currently processing 375-500 GHz prototype using

Nb/AlN/Nb SIS mixer and superconducting hybrid

12Millimeter/THz Development at the NRAO CDL

IF OutputSuperconducting 3dB RF Hybrid

SIS Mixer

SIS Mixer

Superconducting 180° IF Hybrid

Sideband-Separating SIS Mixers

• Reject atmospheric noise in other sideband• Eliminate need for LO frequency switching to identify

spectral lines• Below is shown a balanced and sideband-separating SIS

mixer

13Millimeter/THz Development at the NRAO CDL

Absorbing LoadSuperconducting 3dB RF Hybrids

SIS Mixer

USB IF OutputLSB IF Output

SIS Mixer

SIS Mixer

SIS Mixer

Superconducting 180° IF Hybrids

UVML/NRAO/UAz SIS Collaboration:Recent Highlights• Factor of 10 improvement (from +/- 2 Ang. to +/- 0.2 Ang.)

in repeatability of AlN thickness using new ICP growth protocol and rebuilt

• Succesful implementation of single-resist junction process, quicker and more repeatbale than pentablevel process

• Precise measurements of Nb and NbTiN films London penetration depth

• Room temperature verification 385-500 GHz superconducting hybrid on high-conductivity silicon membrane

14Millimeter/THz Development at the NRAO CDL

UVML/NRAO/UAz SIS Collaboration:Development Plan• March 2011: Repeatable Jc on Nb/Al-AlN/Nb trilayer test

circuits• May 2011: 385-500 GHz SIS wafer complete• June 2011: Single-ended and balanced 385-500 GHz SIS

mixer measured• Summer 2011: Nb/Al-AlN/NbTiN trilayer tests followed by

band 10 SIS fabrication• Fall 2011: Testing of sputtered Nb/AlN/NbTiN,

NbTiN/AlN/NbTiN, hot-deposited NbTiN trilayers

15Millimeter/THz Development at the NRAO CDL