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Studies on radiation detectors using high-Tc superconductors
Physica C 235-240 (1994)3391-3392 North-Holland
PHISIgA
(~
Studies o n radiation detectors using high-Tc superconductors* D. Bloyeta, D. Robbes a, P. Langloisa, A. Gilabertb, I. Aboudihabb, A. Kreislerc, J-M. Depond c, D. Pavuna d, A. Gauzzi d, B. Dwird, J-C. Vill6giere, A. Ghise, A. J~igere and F. Pourtiere aLEI, EA 970 MESR, ISMRa, 6 Bd du Mar6chal Juin, 14050 Caen Cedex, France bLPMC, URA 190 CNRS, Universit6 de Nice-Sophia-Antipolis, 06108 Nice Cedex, France CLGEP, URA 127 CNRS, SUPELEC, Plateau de Moulon, 91192 Gif sur Yvette Cedex, France dlMO +, Dept. of Physics, Ecole Polytechnique F6d6rale de Lausanne, CH 1015, Switzerland eLETI-CEA, Technologies Avanc6es, 17 rue des Martyrs, 38054 Grenoble Cedex 9, France A wide range of photodetectors has been investigated, at various wavelengths and in various time domain operating conditions (from low frequency modulated cw sources to pulsed sources). The most promising devices, which have been realized, optimized (by using theoretical 2D or 3D thermal models) and tested, are described. 1. I N T R O D U C T I O N The discovery of high-Tc materials has revived the interest in radiation detecting applications of superconductors. The main results obtained in this field with (mainly YBCO) thin films by the participants of GECSE* are briefly considered. 2. B O L O M E T R I C D E T E C T I O N 2.1. Fast and sensitive
bolometers Investigations at LEI have been oriented in developing bolometers using an original principle based upon the temperature dependence of an YBCO microbridge critical current lc. The microbridge is biased at constant voltage and a simple control circuit delivers an output voltage proportional to the device current [1]. The data given in table 1 show that the detectivity so obtained is at the level of actual (1993) world records, which can be roughly summarized by the relationship
D*_=1011z 1/2 (D* in cmHzl/2w - 1 , 1 : i n s ) . (1) A 3D thermal model was developed that showed that the thermal flux is only limited by the filmsubstrate resistance, with no lateral diffusion, the MgO substrate remaining isothermal. The resulting response is fast because essentially limited by the YBCO film inertia.
2.2. D e t e c t i o n
with s u p e r l a t t i c e s t r u c t u r e s The photoresponse of YBa2Cu307_5/La2CuO 4 multilayers irradiated at 10.6[.tm (CO2 laser) or 0.83 I.tm (semiconductor laser) radiation were studied at LPMC. The structure (I 31 nm thick) consisted of 6 YBCO layers (11 nm thick) alternating with 5 LCO layers (13 nm thick) deposited by laser ablation on MgO substrates [2]. These multilayers exhibited an unexpected bolometric behaviour as compared to YBCO single layers. The responsivity was larger (by a factor -2) and the modulation frequency response only ~f-0.15 dependent (instead of ~f-0.5, as expected from a strong thermal coupling with the substrate, see § 2.4.). This opens an interesting field of investigations for wide band applications [3].
Table 1. Best performances obtained at LEI with a 0.2x12x60 [tm3 microbridge patterned in an YBCO/MgO film Substrate temperature 84.5 K Radiation wavelength 0.8 I-tm 7.5 mA/K Temperature dependence of I c 80 V/W Voltage responsivity Current responsivity 0.8 A/W 7 nV/~lHz Voltage noise Noise equivalent power (NEP) 87 pW/~/Hz Noise equivalent temp. (NET) 9 nK/~/Hz Specific detectivity D* 3x107 cm~/Hz/W Time constant v 20 ns
* Research program undertaken by GECSE (Groupe d'Etudes des Composants Supraconducteurs en Electronique), to promote the study of superconducting devices for applications to electronics, and with GDR supraconducteurs of CNRS. + With the financial support of the PNR-30 division of the Swiss National Fund for Scientific Research (Bern). 0921-4534/94/$07.00 © 1994- ElsevierScience B.V. All rights reserved. SSDI 0921-4534(94)02261-5
3392
D. Blqvet et al./Physica C 235-240 (1994) 3391 3392
2.3. E l a b o r a t i o n on e c o n o m i c a l substrates YBCO - I gm thick films were obtained at LGEP by rf magnetron sputtering on polycrystalline yttriadoped zirconia substrates and tested at A, = 10 g m . Several detector geometries were fabricated and 2D thermal simulations successfully performed to explain a complex modulation frequency behaviour [4]. 2.4. Ultra-wide wavelength range detectors The essentially wavelength independence of the bolometric effect was demonstrated at IMO with YBCO films ion-beam sputtered on thinned SrTiO 3 substrates [5]. Prototype devices were etched to produce either constriction shaped (20x20 ~tm2) or meander shaped sensitive firms. The former exhibited a responsivity versus chopping frequency response R o~f-0.5, indicating a strong coupling of" the film to the thermal bath, while for the latter the coupling is loose, showing R o~f - I response. The optimum sensitivity was obtained with the meander : R ~ 800 V/W and NEP ~ 5x10 -I1 W/~/Hz.
~. 0.3
........ ,
........ ,
........ ,
........
.,0.16
• • • ....
>>0.14
'
+:40K--'Tc/2
i
~ 0.12
'bias--0mA
4 0 ~
"~ 0.1 ~0.08
006
Win = 10 mJ/pulse
j
/
:o04 i ¢~ 0.02 0'
0
,.,dp,
.
40
80 120 160 200 Time (ps) Figure 2. Response of a 30 nm thick YBCO/MgO microbridge shorting a coplanar waveguide (LETI). 3.2.
New p h o t o t r a n s i s t o r concept Field-effect devices have been built at LETI with YBCO/PBCO multilayers grown on MgO substrates transparent at visible and IR wavelengths (Fig. 3). A good responsivity at A = 633 nm up to 1 MHz modulation frequency was observed. Combination of field-effect and optical irradiation leading to fast nonbolometric effect were observed for the first time.
"~0.1
~ate
= ~ o
T = 90.6 K (compensated lbias = 10 mA for various ,fodin =100Hz beam diameters 0.03 ................ i ........ i . . • 0. 1 10 100 1000 Wavelength (Bin) Figure 1. Voltage responses at various wavelengths of a bolometer for normalized conditions (IMO).
I YBaCuO/PrBaCuO,,~ ~ multilayer channel
substrate (MgO)[ optical irradiation
Figure 3. Configuration of a SUPFET transistor [7]. REFERENCES
3. N O N - B O L O M E T R I C
EFFECTS
3.1. Ultra-fast infrared detectors The LETI has developed ultra-fast IR detectors based on bolometric/non-bolometric phenomena. Electrical photoresponse measurements were performed on Corbino type as well as coplanar line structures obtained by inverted cathode magnetron dc sputtering. They showed (Fig. 2) a very fast inductive reaction (rise time < 12 ps, width - 30 ps) allowing to reconstruct the - 40 ps wide laser pulse shape, followed by the bolometric heating effect significant for the incident energy [6]. The experiments were done either at 2 = 1.06 gm with 300 fs laser pulses or at 2 - 2 0 /am with a free electron laser delivering -100 fs micro-pulses. The influence of bias current, incident power, and operating temperature on the response have been analysed.
1. D. Robbes, P. Langlois, D. Bloyet, C. Dolabdjian, J-F. Hamet and H. Murray, IEEE Trans. Appl. Supercond. 3(I), 2120 (1993). 2. A. Alimoussa, M.J. Casanove, M. Schwerdtfeger, C. Villard and J-C. VillEgier, Physica C 202, 23 (1992). 3. I. Aboudihab, Thesis, Univ. of Nice (1994). 4. J-M. Depond, F. Carri6, J-C. Martin, A. Kreisler, M. Redon, C. Martin and D. T6tard, presented at M2S-SHTC IV, (July 1994). 5. B. Dwir and D. Pavuna, J. Appl. Phys. 72(9), 3855 (1992). 6. A. Ghis, J-C. Vill6gier, M. Nail, Ph. Gibert and S. Striby, Proc. OE/'LASE'94, SPIE Vol. 2159, (June 1994). 7. A. Jfiger, F. Pourtier and J-C. Villdgier, Proc. OE/'LASE'94, SPIE Vol. 2160, (June 1994).
PHISIgA
(~
Studies o n radiation detectors using high-Tc superconductors* D. Bloyeta, D. Robbes a, P. Langloisa, A. Gilabertb, I. Aboudihabb, A. Kreislerc, J-M. Depond c, D. Pavuna d, A. Gauzzi d, B. Dwird, J-C. Vill6giere, A. Ghise, A. J~igere and F. Pourtiere aLEI, EA 970 MESR, ISMRa, 6 Bd du Mar6chal Juin, 14050 Caen Cedex, France bLPMC, URA 190 CNRS, Universit6 de Nice-Sophia-Antipolis, 06108 Nice Cedex, France CLGEP, URA 127 CNRS, SUPELEC, Plateau de Moulon, 91192 Gif sur Yvette Cedex, France dlMO +, Dept. of Physics, Ecole Polytechnique F6d6rale de Lausanne, CH 1015, Switzerland eLETI-CEA, Technologies Avanc6es, 17 rue des Martyrs, 38054 Grenoble Cedex 9, France A wide range of photodetectors has been investigated, at various wavelengths and in various time domain operating conditions (from low frequency modulated cw sources to pulsed sources). The most promising devices, which have been realized, optimized (by using theoretical 2D or 3D thermal models) and tested, are described. 1. I N T R O D U C T I O N The discovery of high-Tc materials has revived the interest in radiation detecting applications of superconductors. The main results obtained in this field with (mainly YBCO) thin films by the participants of GECSE* are briefly considered. 2. B O L O M E T R I C D E T E C T I O N 2.1. Fast and sensitive
bolometers Investigations at LEI have been oriented in developing bolometers using an original principle based upon the temperature dependence of an YBCO microbridge critical current lc. The microbridge is biased at constant voltage and a simple control circuit delivers an output voltage proportional to the device current [1]. The data given in table 1 show that the detectivity so obtained is at the level of actual (1993) world records, which can be roughly summarized by the relationship
D*_=1011z 1/2 (D* in cmHzl/2w - 1 , 1 : i n s ) . (1) A 3D thermal model was developed that showed that the thermal flux is only limited by the filmsubstrate resistance, with no lateral diffusion, the MgO substrate remaining isothermal. The resulting response is fast because essentially limited by the YBCO film inertia.
2.2. D e t e c t i o n
with s u p e r l a t t i c e s t r u c t u r e s The photoresponse of YBa2Cu307_5/La2CuO 4 multilayers irradiated at 10.6[.tm (CO2 laser) or 0.83 I.tm (semiconductor laser) radiation were studied at LPMC. The structure (I 31 nm thick) consisted of 6 YBCO layers (11 nm thick) alternating with 5 LCO layers (13 nm thick) deposited by laser ablation on MgO substrates [2]. These multilayers exhibited an unexpected bolometric behaviour as compared to YBCO single layers. The responsivity was larger (by a factor -2) and the modulation frequency response only ~f-0.15 dependent (instead of ~f-0.5, as expected from a strong thermal coupling with the substrate, see § 2.4.). This opens an interesting field of investigations for wide band applications [3].
Table 1. Best performances obtained at LEI with a 0.2x12x60 [tm3 microbridge patterned in an YBCO/MgO film Substrate temperature 84.5 K Radiation wavelength 0.8 I-tm 7.5 mA/K Temperature dependence of I c 80 V/W Voltage responsivity Current responsivity 0.8 A/W 7 nV/~lHz Voltage noise Noise equivalent power (NEP) 87 pW/~/Hz Noise equivalent temp. (NET) 9 nK/~/Hz Specific detectivity D* 3x107 cm~/Hz/W Time constant v 20 ns
* Research program undertaken by GECSE (Groupe d'Etudes des Composants Supraconducteurs en Electronique), to promote the study of superconducting devices for applications to electronics, and with GDR supraconducteurs of CNRS. + With the financial support of the PNR-30 division of the Swiss National Fund for Scientific Research (Bern). 0921-4534/94/$07.00 © 1994- ElsevierScience B.V. All rights reserved. SSDI 0921-4534(94)02261-5
3392
D. Blqvet et al./Physica C 235-240 (1994) 3391 3392
2.3. E l a b o r a t i o n on e c o n o m i c a l substrates YBCO - I gm thick films were obtained at LGEP by rf magnetron sputtering on polycrystalline yttriadoped zirconia substrates and tested at A, = 10 g m . Several detector geometries were fabricated and 2D thermal simulations successfully performed to explain a complex modulation frequency behaviour [4]. 2.4. Ultra-wide wavelength range detectors The essentially wavelength independence of the bolometric effect was demonstrated at IMO with YBCO films ion-beam sputtered on thinned SrTiO 3 substrates [5]. Prototype devices were etched to produce either constriction shaped (20x20 ~tm2) or meander shaped sensitive firms. The former exhibited a responsivity versus chopping frequency response R o~f-0.5, indicating a strong coupling of" the film to the thermal bath, while for the latter the coupling is loose, showing R o~f - I response. The optimum sensitivity was obtained with the meander : R ~ 800 V/W and NEP ~ 5x10 -I1 W/~/Hz.
~. 0.3
........ ,
........ ,
........ ,
........
.,0.16
• • • ....
>>0.14
'
+:40K--'Tc/2
i
~ 0.12
'bias--0mA
4 0 ~
"~ 0.1 ~0.08
006
Win = 10 mJ/pulse
j
/
:o04 i ¢~ 0.02 0'
0
,.,dp,
.
40
80 120 160 200 Time (ps) Figure 2. Response of a 30 nm thick YBCO/MgO microbridge shorting a coplanar waveguide (LETI). 3.2.
New p h o t o t r a n s i s t o r concept Field-effect devices have been built at LETI with YBCO/PBCO multilayers grown on MgO substrates transparent at visible and IR wavelengths (Fig. 3). A good responsivity at A = 633 nm up to 1 MHz modulation frequency was observed. Combination of field-effect and optical irradiation leading to fast nonbolometric effect were observed for the first time.
"~0.1
~ate
= ~ o
T = 90.6 K (compensated lbias = 10 mA for various ,fodin =100Hz beam diameters 0.03 ................ i ........ i . . • 0. 1 10 100 1000 Wavelength (Bin) Figure 1. Voltage responses at various wavelengths of a bolometer for normalized conditions (IMO).
I YBaCuO/PrBaCuO,,~ ~ multilayer channel
substrate (MgO)[ optical irradiation
Figure 3. Configuration of a SUPFET transistor [7]. REFERENCES
3. N O N - B O L O M E T R I C
EFFECTS
3.1. Ultra-fast infrared detectors The LETI has developed ultra-fast IR detectors based on bolometric/non-bolometric phenomena. Electrical photoresponse measurements were performed on Corbino type as well as coplanar line structures obtained by inverted cathode magnetron dc sputtering. They showed (Fig. 2) a very fast inductive reaction (rise time < 12 ps, width - 30 ps) allowing to reconstruct the - 40 ps wide laser pulse shape, followed by the bolometric heating effect significant for the incident energy [6]. The experiments were done either at 2 = 1.06 gm with 300 fs laser pulses or at 2 - 2 0 /am with a free electron laser delivering -100 fs micro-pulses. The influence of bias current, incident power, and operating temperature on the response have been analysed.
1. D. Robbes, P. Langlois, D. Bloyet, C. Dolabdjian, J-F. Hamet and H. Murray, IEEE Trans. Appl. Supercond. 3(I), 2120 (1993). 2. A. Alimoussa, M.J. Casanove, M. Schwerdtfeger, C. Villard and J-C. VillEgier, Physica C 202, 23 (1992). 3. I. Aboudihab, Thesis, Univ. of Nice (1994). 4. J-M. Depond, F. Carri6, J-C. Martin, A. Kreisler, M. Redon, C. Martin and D. T6tard, presented at M2S-SHTC IV, (July 1994). 5. B. Dwir and D. Pavuna, J. Appl. Phys. 72(9), 3855 (1992). 6. A. Ghis, J-C. Vill6gier, M. Nail, Ph. Gibert and S. Striby, Proc. OE/'LASE'94, SPIE Vol. 2159, (June 1994). 7. A. Jfiger, F. Pourtier and J-C. Villdgier, Proc. OE/'LASE'94, SPIE Vol. 2160, (June 1994).