THz detector arrays M Sakhno J GumenjukSichevska F Sizov Institute of Semiconductor Physics NASU Kiev Ukraine email sakhnomgmailcom THz CMOS FPA principle Advantages ID: 813125
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Slide1
How to achieve a homogeneous sensitivity in THz detector arrays
M.
Sakhno
, J.
Gumenjuk-Sichevska
, F.
Sizov
Institute of Semiconductor Physics NASU,
Kiev, Ukraine,
e-mail: sakhno.m@gmail.com
Slide2THz CMOS FPA principleAdvantages of Si FET THz Detectors Based on standard silicon technology with high level of integration
Un-cooled
Can be assembled into arrays for real time THz/mm wave imaging;
Mechanically robust;Low costs at high volumes
2
Antenna
FET
Slide3Detector characterization
Uniform NEP for different
elements of the array
Minimal NEP
Goal
1. Maximal G and
η
a
2. Uniform
G and
η
aNEP – noise equivalent power. Minimal power which can be detected by detector
NEPel electrical NEP of detector itselfG the antenna gainηa matching between the antenna and the detector
3
Slide4System photograph (silicon FET array implementation)
Printed antennas on finite electrically thick substrate
Modelled system
4
Slide5System parameters
10
75.8
164
20
104
Modeling using EMSS
FEKO
10
mm
1
mm
1
mm
The modeled system design:
8
antennas on a substrate of finite size. Antennas are positioned symmetrically relative to the substrate center
5
Slide6Cut-off frequency of the first mode fc1 for infinite substrate
h, µm
ε
r
=2
ε
r
=7
ε
r
=12
501.5THz
0.612 THz0.452 THz140
0.536 THz
0.219 THz
0.162 THz6500.116 THz
0.047 THz0.035 THz
Pozar, D.: Considerations for millimeter
wave printed antennas. IEEE Trans. Antennas Propag. 31, 740–747 (1983)
6
Slide7Linear gain diagram for
substrate
thickness
h=50
μm
, f=300GHz
Each antenna was simulated and the results were combined on one picture to facilitate the comparison of different elements
7
Slide8Linear gain diagram for substrate thickness h=140 μm, f=300GHz
8
Slide9Linear gain diagram for substrate thickness h=650 μm, f=300GHz
9
Slide10Antenna pattern for different substrate relative
permittivities
Substrate thickness is h=140
μm
10
Slide11Dependence of the calculated total antenna gain G in the normal direction on the substrate permittivity
1
2
3
4
5
6
7
8
11
Slide12Calculated gain for normal direction for 1st and 4th elements
1
2
3
4
5
6
7
8
12
Slide13Antenna – transistor matching
Antenna
FET
R
G
= 150 Ω,
R
S
= 50 Ω,
C
p
= 4
fF
Z
tr
= (200 – j
130)
Ω at f
= 300 GHz
13
1-μm Si MOSFETW/L = 20/2 (μm)
Sakhno
, M.,
Golenkov
, A., &
Sizov
, F. (2013). Uncooled detector challenges:
Millimeter
-wave and terahertz long channel field effect transistor and
Schottky
barrier diode detectors.
Journal of Applied Physics
,
114
(16), 164503. doi:10.1063/1.4826364
Slide14Antenna-detector matching for different substrate thickness
1
2
3
4
5
6
7
8
Optimal matching is not for electrically thinnest substrate
Matching coefficient variation is less than gain variation
14
Slide15System with the lens
The angle of maximum gain versus the element position for the system with the lens (only the first four elements are shown because of the mirror symmetry). The substrate parameters are
h
=50
μm
,
r
=2, the incident radiation frequency is 300 GHz
15
Slide16ConclusionsThe substrate electric thickness in THz FPAs plays a crucial role in the frequency characteristics of the systemElectrically thick substrate makes NEP of elements non-uniformDegradation of antenna pattern can be explained by excitation of substrate modes. Critical substrate thickness is approximately 0.25 wavelength in dielectricSimulation shows that Si CMOS system (substrate thickness
h
= 50μm and
εr = 2) with the lens can operate as FPA16
Slide17AcknowledgementsThis work is partly supported by the SPS:NUKR.SFP 984544 Project and a joint grant 01-02-2012 from the National Academy of Sciences of Ukraine and Russian Academy of Sciences.17
Slide18Thank You !18