Browsing by Subject "Infrared detector"

Now showing 1 - 6 of 6

Open Access
Electronic and optical properties of 4.2 lm‘‘N’’ structured superlattice MWIR photodetectors
(Elsevier B.V., 2013-01-05) Salihoglu, O.; Hostut M.; Tansel, T.; Kutluer, K.; Kilic A.; Alyoruk, M.; Sevik, C.; Turan, R.; Ergun, Y.; Aydınlı, Atilla
We report on the development of a new structure for type II superlattice photodiodes that we call the ‘‘N’’ design. In this new design, we insert an electron barrier between InAs and GaSb in the growth direction. The barrier pushes the electron and hole wavefunctions towards the layer edges and under bias, increases the overlap integral by about 25% leading to higher detectivity. InAs/AlSb/GaSb superlattices were studied with density functional theory. Both AlAs and InSb interfaces were taken into account by calculating the heavy hole–light hole (HH–LH) splittings. Experiments were carried out on single pixel photodiodes by measuring electrical and optical performance. With cut-off wavelength of 4.2 lm at 120 K, temperature dependent dark current and detectivity measurements show that the dark current is 2.5 10 9 A under zero bias with corresponding R0A resistance of 1.5 104 X cm2 for the 500 500 lm2 single pixel square photodetectors. Photodetector reaches BLIP condition at 125 K with the BLIP detectivity (D BLIP) of 2.6 1010 Jones under 300 K background and 0.3 V bias voltage.
Open Access
Electronic and optical properties of 4.2 μm"N" structured superlattice MWIR photodetectors
(Elsevier, 2013) Salihoglu, O.; Hostut M.; Tansel, T.; Kutluer, K.; Kilic A.; Alyoruk, M.; Sevik, C.; Turan, R.; Ergun, Y.; Aydınlı, Atilla
We report on the development of a new structure for type II superlattice photodiodes that we call the "N" design. In this new design, we insert an electron barrier between InAs and GaSb in the growth direction. The barrier pushes the electron and hole wavefunctions towards the layer edges and under bias, increases the overlap integral by about 25% leading to higher detectivity. InAs/AlSb/GaSb superlattices were studied with density functional theory. Both AlAs and InSb interfaces were taken into account by calculating the heavy hole-light hole (HH-LH) splittings. Experiments were carried out on single pixel photodiodes by measuring electrical and optical performance. With cut-off wavelength of 4.2 μm at 120 K, temperature dependent dark current and detectivity measurements show that the dark current is 2.5 × 10 -9 A under zero bias with corresponding R0A resistance of 1.5 × 104 Ω cm2 for the 500 × 500 μm2 single pixel square photodetectors. Photodetector reaches BLIP condition at 125 K with the BLIP detectivity (DBLIP) of 2.6 × 10 10 Jones under 300 K background and -0.3 V bias voltage. © 2012 Elsevier B.V. All rights reserved.
Open Access
İnvestigation, modeling, and applications feasibility of the thermal crosstalk in high Tc transition edge bolometer arrays
(2006) Bozbey, Ali
So far, the high Tc transition edge bolometer (TEB) devices are mostly used as single pixel detectors. Recently, there are a number of groups working on the 2-4 pixel array applications of the high Tc TEB. Though the target spectrum of the TEB is far IR and mm-waves, we are using a near IR laser source in our investigation due to practical reasons since the response analysis is similar. We have designed and implemented 4-pixel Y Ba2Cu3O7−δ (YBCO) edge transition bolometer arrays. The crosstalk study was made possible through the illumination of the sense-devices and measuring the voltage response of the blocked read-out device in the same array. This was done using a silver coated shadow mask. In order to prevent thermal artifacts created by the mask, the mask was made in free standing configuration on top of the devices. The devices were made of 200 nm and 400 nm thick pulsed laser deposited YBCO films on SrT iO3 and LaAl2O3 substrate materials. In this thesis, we made the qualitative investigation of the dependence of the thermal crosstalk on the various device parameters such as the substrate material, device layout, YBCO film thickness, operating temperature, and modulation frequency. Then, based on the experimental results, we proposed an analytical thermal model. We proposed two models: i) Basic model, which takes into account only the lateral heat diffusion in the substrate for quick design purposes ii)Analytical model, which takes into account the lateral heat diffusion, vertical heat diffusion, and the effect of the leaking laser radiation through the shadow mask, for detailed design purposes and verifying the qualitative analysis. Finally, we proposed and verified possible applications of the thermal crosstalk in TEB arrays. One proposed application of the crosstalk is the electrical free read-out of the sense pixels by utilization of the unique dependence of the magnitude and phase of the response on the thermal crosstalk between bolometer pixels in an array. The qualitative investigation made in this study is the most detailed investigation about the bolometer arrays and the proposed analytical model is the strongest among the reported ones so far in terms of fitting the experimental results, explaining the effects of the various parameters, and designing TEB arrays. The proposed crosstalk based read-out method is expected to decrease the read-out circuitry for possible TEB based applications. Since multilayer process is difficult to make in high Tc superconductors, decreasing the complexity of the read-out circuitry by half is even important and it is the first time that such a method is utilized including bolometer arrays made of different types of materials.
Open Access
N-structure based on InAs/AlSb/GaSb superlattice photodetectors
(Academic Press, 2015) Hostut, M.; Alyoruk, M.; Tansel, T.; Kilic, A.; Turan, R.; Aydınlı, Atilla; Ergun, Y.
We have studied the theoretical and experimental properties of InAs/AlSb/GaSb based type-II superlattice (T2SL) pin photodetector called N-structure. Electronic properties of the superlattice such as HH-LH splitting energies was investigated using first principles calculations taking into account InSb and AlAs as possible interface transition alloys between AlSb/InAs layers and individual layer thicknesses of GaSb and InAs. T2SL N-structure was optimized to operate as a MWIR detector based on these theoretical approaches tailoring the band gap and HH-LH splitting energies with InSb transition layers between InAs/AlSb interfaces. Experimental results show that AlSb layers in the structure act as carrier blocking barriers reducing the dark current. Dark current density and R0A product at 125 K were obtained as 1.8 × 10-6 A cm-2 and 800ωcm2 at zero bias, respectively. The specific detectivity was measured as 3 × 1012 Jones with cut-off wavelengths of 4.3 μm at 79 K reaching to 2 × 109 Jones and 4.5 μm at 255 K. ©2014 Elsevier Ltd. All rights reserved.
Open Access
Substrate and device pattern dependence of the thermal crosstalk in Y Ba2Cu 3O7−δ transition edge bolometer arrays
(Institute of Electrical and Electronics Engineers, 2006-12) Bozbey, A.; Fardmanesh, M.; Schubert, J.; Banzet, M.
Using YBa2CU3O7-delta (YBCO) thin films, pulsed laser deposited on 1-mm-thick LaAlO3 or SrTiO3 substrates, we made 4 x 1 pixel arrays of transition edge bolometers with separations between neighboring pixels ranging from 40 mu m to 170 mu m for testing purposes. We investigated the effects of the YBCO film thickness (200 and 400 nm), substrate material, and back-etching of the substrate, on the crosstalk between the pixels of the arrays. The investigation was based on the analysis of the voltage response of the de current biased bolometers versus the modulation frequency of a near-infrared laser source. We observed that the bolometer arrays made of 400-nm-thick films had less interpixel thermal crosstalk than the 200-nm-thick films. The effect of substrate thickness on the response of the pixels was investigated by up to 500 mu m back-etching of the substrates. The bolometers made on back-etched LaAlO3 substrates had anomalous crosstalk response behavior, which was effective at higher modulation frequencies. In addition, we present an analytical thermal model for explaining the observed effects of the thermal crosstalk on the response characteristics of the pixels of the arrays. We report the measured response and the anticipated thermal crosstalk of the characterized bolometers'. We describe the responses based on the thermal models and discrepancies from the model's predictions.
Open Access
Superconductivity transition dependence of the thermal crosstalk in YBa 2Cu 3O 7-x edge-transition bolometer arrays
(Institute of Electrical and Electronics Engineers, 2006) Bozbey, A.; Fardmanesh, M.; Schubert, J.; Banzet, M.
The effect of the superconductivity transition on the thermal crosstalk in YBa 2Cu 3O 7-x, edge-transition bolometer arrays is investigated for DC to midrange modulation frequency infrared radiation. The bolometers in the arrays were designed with various distances on SrTiO 3 (100) substrates. We have observed a change in the thermal crosstalk between neighbor devices through the superconductivity transition temperature range. Superconductivity transition dependence of the thermal coupling between the devices was measured by utilizing the thermal conductance measurement methods developed for the bulk material. The knee points in the magnitude of the response versus modulation frequency curves of the devices were also determined by illuminating one of the bolometers in the arrays and measuring the response of the neighbor devices. By using the knee frequency and the distance between the bolometers, the modulation frequency criterion for crosstalk-free response at the transition region in various array structures is found and the results of the thermal coupling measurements are further studied and presented here.