NASA Technical Reports Server (NTRS) 20090008431: Submillimeter-Wave Amplifier Module with Integrated Waveguide Transitions

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by  NASA Technical Reports Server (NTRS)

SiC Optically Modulated Field-Effect Transistor
Such transistors could be useful as ultraviolet detectors.
John H. Glenn Research Center, Cleveland, Ohio
An optically modulated field-effect could be considerably greater than that The exact physical mechanism of
transistor (OFET) based on a silicon of a photodiode, such that the need for modulation of conductivity is a subject
carbide junction field-effect transistor amplification external to the photode- of continuing research. It is known that
(JFET) is under study as, potentially, a tector could be reduced or eliminated. injection of minority charge carriers (in
prototype of devices that could be use- The experimental SiC OFET was made this case, holes) at the interface exerts a
ful for detecting ultraviolet light. The by processes similar to JFET-fabrication strong effect on the channel, resulting
SiC OFET is an experimental device processes developed at Glenn Research in amplification of the photon-detec-
that is one of several devices, including Center. The gate of the OFET is very tion signal. A family of operating curves
commercial and experimental photodi- long, wide, and thin, relative to the gates characterizing the OFET can be gener-
odes, that were initially evaluated as de- of typical prior SiC JFETs. Unlike in prior ated in a series of measurements per-
tectors of ultraviolet light from combus- SiC FETs, the gate is almost completely formed at different intensities of inci-
tion and that could be incorporated transparent to near-ultraviolet and visible dent ultraviolet light.
into SiC integrated circuits to be de- light. More specifically: This work was done by Massood Tabib-Azar
signed to function as combustion sen- (cid:129) The OFET includes a p+gate layer less of Case Western Reserve University for Glenn
sors. The ultraviolet-detection sensitivity than 1/4 µm thick, through which Research Center. Further information is con-
of the photodiodes was found to be less photons can be transported efficiently tained in a TSP (see page 1).
than desired, such that it would be nec- to the p+/p body interface. Inquiries concerning rights for the com-
essary to process their outputs using (cid:129) The gate is relatively long and wide mercial use of this invention should be ad-
high-gain amplification circuitry. On (about 0.5 by 0.5 mm), such that holes dressed to NASA Glenn Research Center, In-
the other hand, in principle, the func- generated at the body interface form a novative Partnerships Office, Attn: Steve
tion of the OFET could be character- depletion layer that modulates the Fedor, Mail Stop 4–8, 21000 Brookpark
ized as a combination of detection and conductivity of the channel between Road, Cleveland, Ohio 44135. Refer to
amplification. In effect, its sensitivity the drain and the source. LEW-18349-1
Submillimeter-Wave Amplifier Module With Integrated
Waveguide Transitions
This technique can be used in submillimeter-wave imaging in homeland security, weapons
detection, and commercial test equipment.
NASA’s Jet Propulsion Laboratory, Pasadena, California
To increase the usefulness of mono- stage. Wire bonds from the DC drain
lithic millimeter-wave integrated circuit and gate pads are connected to off-
(MMIC) components at submillimeter- chip shunt 51-pF capacitors, and addi-
wave frequencies, a chip has been de- tional off-chip capacitors and resistors
signed that incorporates two integrated, are added to the gate and drain bias
radial E-plane probes with an MMIC am- lines for low-frequency stability of the
plifier in between, thus creating a fully amplifier. Additionally, bond wires to
integrated waveguide module. The inte- DC Bias the grounded coplanar waveguide
grated amplifier chip has been fabri- Board pads at the RF input and output of the
cated in 35-nm gate length InP high- internal amplifier are added to ensure
electron-mobility-transistor (HEMT) good ground connections to the wave-
technology. The radial probes were guide package.
mated to grounded coplanar waveguide Input Output The S-parameters of the module, not
input and output lines in the internal waveguide Waveguide corrected for input or output wave-
amplifier. The total length of the inter- guide loss, are measured at the wave-
nal HEMT amplifier is 550 µm, while Clip Cavity guide flange edges. The amplifier mod-
the total integrated chip length is 1,085 ule has over 10 dB of gain from 290 to
µm. The chip thickness is 50 µm with 330 GHz, with a peak gain of over 14
the chip width being 320 µm. dB at 307 GHz. The WR2.2 waveguide
The internal MMIC amplifier is bi- cutoff is again observed at 268 GHz.
ased through wire-bond connections The module is biased at a drain current
to the gates and drains of the chip. of 27 mA, a drain voltage of 1.24 V, and
A photograph of the Split-Block Module, showing
The chip has 3 stages, emp loying 35- a gate voltage of +0.21 V. Return loss of
the input and output waveguide, chip cavity, and DC
nm gate length transistors in each bias board. the module is very good between 5 to
12 NASA Tech Briefs, January 2009
25 dB. This result illustrates the useful- homeland security, hidden weapons Fung of Caltech and William Deal, Gerry
ness of the integrated radial probe tran- detection, airport security, detection Mei, Vesna Radisic, and Richard Lai of
sition, and the wide (over 10-percent) of bio-weapons, as well as potential ap- Northrop Grumman Corporation for
bandwidth that one can expect for am- plications in commercial test equip- NASA’s Jet Propulsion Laboratory. The con-
plifier modules with integrated radial ment. This technology is partially a tributors would like to acknowledge the sup-
probes in the submillimeter-regime semiconductor chip product and par- port of Dr. Mark Rosker and the Army Re-
(>300 GHz). tially a waveguide module. The semi- search Laboratory. This work was supported
This technology was developed for a conductor is not fixed in its final form, by the DARPA SWIFT Program and Army
submillimeter-wave imaging system but the module is essentially fixed in Research Laboratory under the DARPA
under the DARPA SWIFT program, in its final form. MIPR no. 06-U037 and ARL Contract no.
collaboration with Northrop Grum- This work was done by Lorene Samoska, W911QX-06-C-0050. Further information
man Corporation. Submillimeter-wave Goutam Chattopadhyay, David Pukala, is contained in a TSP (see page 1). NPO-
imaging has many applications to Todd Gaier, Mary Soria, and King Man 45088
Metrology System for a Large, Somewhat Flexible Telescope
This system would measure focal-plane position errors caused by structural deformations.
NASA’s Jet Propulsion Laboratory, Pasadena, California
A proposed metrology system would
be incorporated into a proposed tele-
Distant Object
scope that would include focusing optics
Observed by Telescope
on a rigid bench connected via a deploy-
able mast to another rigid bench hold-
ing a focal-plane array of photon count-
ing photodetectors. Deformations of the
deployable mast would give rise to opti-
Focusing Optics of Telescope
cal misalignments that would alter the
directions (and, hence, locations) of in-
cidence of photons on the focal plane. Metrology
Bench
The metrology system would measure System
the relative displacement of the focus-
Diode Laser
ing-optics bench and the focal-plane
array bench. The measurement data Laser Beam Mast or
would be used in post-processing of the Other Flexible
Telescope
digitized photodetector outputs to com- Structural Photodetector Array
pensate for the mast-deformation-in- Position-Sensitive Member
duced changes in the locations of inci- Photodiode
dence of photons on the focal plane,
thereby making it possible to determine Bench
the original directions of incidence of
photons with greater accuracy.
This Deformation of the Mastwould change the position of incidence of the laser beam on the posi-
The proposed metrology system is de- tion-sensitive photodiode.
signed specifically for the Nuclear Spec-
troscopic Telescope Array (NuSTAR) a shown in the figure, which is a greatly tion-sensitive photodiode. For each
proposed spaceborne x-ray telescope. simplified schematic diagram of the metrology reading, the output of the
The basic principles of design and oper- system. Each laser would be aimed at a position-sensitive detector would be
ation are also applicable to other large, position-sensitive photodiode that sampled and digitized twice: once with
somewhat flexible telescopes, both ter- would be mounted on the detector the lasers turned on, then once with
restrial and spaceborne. In the NuSTAR, bench alongside the aforementioned the lasers turned off. The data from
the structural member connecting the telescope photodetector array. The these two sets of samples would be sub-
optical bench and the photodetector diode lasers would operate at a wave- tracted from each other to further re-
array would be a 10-m-long deployable length of 830 nm, each at a power of duce the effects of sun glints or other
mast, and there is a requirement to keep 200 mW. Each laser beam would be fo- background light sources.
errors in measured directions of inci- cused to a spot of ≈1-mm diameter on This work was done by Carl Christian
dence of photons below 10 arc seconds the corresponding position-sensitive Liebe, Randall Bartman, and Walter Cook of
(3 sigma). photodiode. To reduce the effect of Caltech and William Craig of Lawrence Liv-
The proposed system would include sunlight on the measurements, a one- ermore National Laboratory for NASA’s Jet
three diode lasers that would be stage light baffle and an 830-nm trans- Propulsion Laboratory. Further information
mounted on the focusing-optics mission filter of 10-nm bandwidth is contained in a TSP (see page 1).NPO-
bench. For clarity, only one laser is would be placed in front of the posi- 44119
NASA Tech Briefs, January 2009 13