Browsing by Subject "InAs/GaSb"

Now showing 1 - 9 of 9

Open Access
Effect of the passivation layer on the noise characteristics of mid-wave-infrared InAs / GaSb superlattice photodiodes
(IEEE, 2012) Tansel, T.; Kutluer, K.; Salihoglu, Ö.; Aydınlı, Atilla; Aslan, B.; Arikan, B.; Kilinc, M. C.; Ergun, Y.; Serincan, U.; Turan, R.
The authors describe the noise characterization of a mid-wavelength- infrared (MWIR) photodiode based on indium arsenide and gallium antimonide (InAs/GaSb) superlattice (SL), addressing the influence of different passivation layers applied to the surface of the device. The MWIR InAs/GaSb SL design structure is based on p-i-n configuration grown by the molecular beam epitaxy on a (001) n-GaSb substrate. The SiO 2-passivated SL photodiodes demonstrated a Schottky-limited noise up to a bias voltage of -0.1 V where the measured peak responsivity is 1.37 A/W with a cut-off wavelength of 4.9 μm and the specific detectivity as high as 1.23 × 10 12 cm. Hz 1/2 W , demonstrating the high quality of the fabricated MWIR SL photodiodes. The noise measurements exhibited a frequency-dependent plateau (i.e., 1/f noise) for unpassivated and Si 3N 4-passivated samples, whereas 1/f-type noise suppression (i.e., frequency-independent plateau) with a noise current reduction at about 30 Hz of more than one order of magnitude was observed for the SiO 2-passivated ones.
Open Access
Gibbs free energy assisted passivation layers
(SPIE, 2016) Salihoğlu, Ömer; Tansel, T.; Hoştut, M.; Ergun, Y.; Aydınlı, Atilla
Reduction of surface leakage is a major challenge in most photodetectors that requires the elimination of surface oxides on etched mesas during passivation. Engineering the passivation requires close attention to chemical reactions that take place at the interface during the process. In particular, removal of surface oxides may be controlled via Gibbs reactivity. We have compared electrical performance of type-II superlattice photodetectors, designed for MWIR operation, passivated by different passivation techniques. We have used ALD deposited Al2O3, HfO2, TiO2, ZnO, PECVD deposited SiO2, Si3N4 and sulphur containing octadecanethiol (ODT) selfassembled monolayers (SAM) passivation layers on InAs/GaSb p-i-n superlattice photodetectors with cutoff wavelength at 5.1 μm. In this work, we have compared the result of different passivation techniques which are done under same conditions, same epitaxial structure and same fabrication processes. We have found that ALD deposited passivation is directly related to the Gibbs free energy of the passivation material. Gibbs free energies of the passivation layer can directly be compared with native surface oxides to check the effectiveness of the passivation layer before the experimental study.
Open Access
High performance 15-μm pitch 640 × 512 MWIR InAs/GaSb type-II superlattice sensors
(IEEE, 2021-11-18) Oğuz, Fikri; Ülker, E.; Arslan, Y.; Nuzumlali, Ö. L.; Bek, Alpan; Özbay, Ekmel
We report the high performance of Mid-wave Infrared Region (MWIR) InAs/GaSb Type-II Superlattice (T2SL) sensors with $640\times512$ format and 15- $\mu \text{m}$ pixel pitch at both Focal Plane Array (FPA) and pixel level. The p-intrinsic-Barrier-n epilayer structure is adopted for this study, which is grown on 620 ± $30~ \mu \text{m}$ thick GaSb substrate and highly-doped GaSb cap layer at the top structure. The mesa type pixels with sizes of $220\,\,\mu \text{m}\,\,\times 220\,\,\mu \text{m}$ have dark currents $7.8\times10$ −12 A at 77 K both of which are equivalent to state-of-the-art values for Type-II Superlattice sensors. The various passivation techniques to lower the dark current are applied and the results are given in terms of dark current. Electro-optical measurements yielded comparable results to literature. After gathering data and optimizing the fabrication conditions, the FPA of 15- $\mu \text{m}$ pitch having $4.92~ \mu \text{m}$ cut-off wavelength ( $\lambda _{\mathrm {c}}$ ) shows 1.6 A/W peak responsivity, Noise Equivalent Temperature Difference (NETD) of 22.6 mK with optics of f/2.3, quantum efficiency larger than 65% and 99.75% operability. The acquired images by using aforementioned FPA device is presented in this paper. With the reduction of dark current, an encouraging imaging performance is obtained which shows the potential of the Type-II Superlattice detectors in 3 rd generation infrared sensors.
Open Access
High quantum efficiency Type-II superlattice N-structure photodetectors with thin intrinsic layers
(SPIE, 2013) Ergun, Y.; Hostut, M.; Tansel, T.; Muti, bdullah; Kilic, A.; Turan, R.; Aydınlı, Atilla
We report on the development of InAs/AlSb/GaSb based N-structure superlattice pin photodiode. In this new design, AlSb layer in between InAs and GaSb layers acts as an electron barrier that pushes electron and hole wave functions towards the GaSb/InAs interface to perform strong overlap under reverse bias. Experimental results show that, with only 20 periods of intrinsic layers, dark current density and dynamic resistance at -50 mV bias are measured as 6×10-3 A/cm2 and 148 ωcm2 at 77K, respectively. Under zero bias, high spectral response of 1.2A/W is obtained at 5 μm with 50% cut-off wavelengths (λc) of 6 μm. With this new design, devices with only 146 nm thick i-regions exhibit a quantum efficiency of 42% at 3 μm with front-side illimunation and no anti-reflection coatings. © 2013 SPIE.
Open Access
Low dark current N structure superlattice MWIR photodetectors
(SPIE, 2014) Salihoğlu, O.; Muti, Abdullah; Turan, R.; Ergun, Y.; Aydınlı, Atilla
Commercially available read out integrated circuits (ROICs) require the FPA to have high dynamic resistance area product at zero bias (R0A) which is directly related to dark current of the detector. Dark current arises from bulk and surface contributions. Recent band structure engineering studies significantly suppressed the bulk contribution of the type-II superlattice infrared photodetectors (N structure, M structure, W structure). In this letter, we will present improved dark current results for unipolar barrier complex supercell superlattice system which is called as "N structure". The unique electronic band structure of the N structure increases electron-hole overlap under bias, significantly. N structure aims to improve absorption by manipulating electron and hole wavefunctions that are spatially separated in T2SLs, increasing the absorption while decreasing the dark current. In order to engineer the wavefunctions, we introduce a thin AlSb layer between InAs and GaSb layers in the growth direction which also acts as a unipolar electron barrier. Despite the difficulty of perfect lattice matching of InAs and AlSb, such a design is expected to reduce dark current. Experiments were carried out on Single pixel with mesa sizes of 100 × 100 - 700 × 700 μm photodiodes. Temperature dependent dark current with corresponding R0A resistance values are reported.
Open Access
Low-frequency noise behavior at reverse bias region in InAs/GaSb superlattice photodiodes on mid-wave infrared
(SPIE, 2013) Tansel, T.; Kutluer, K.; Muti, Abdullah; Salihoğlu, Ömer; Aydınlı, Atilla; Turan, R.
We describe a relationship between the noise characterization and activation energy of InAs/GaSb superlattice Mid- Wavelength-Infrared photodiodes for different passivation materials applied to the device. The noise measurements exhibited a frequency dependent plateau (i.e. 1/f-noise characteristic) for unpassivated as well as Si3N4 passivated samples whereas 1/f-type low noise suppression (i.e. frequency independent plateau) with a noise current reduction of more than one order of magnitude was observed for SiO2 passivation. For reverse bias values below -0.15V, the classical Schottky-noise calculation alone did not appear to describe the noise mechanism in a SL noise behavior, which shows a divergence between theoretically and experimentally determined noise values. We identify that, the additional noise appears, with and without passivation, at the surface activation energy of < 60 meV and is inversely proportional to the reverse bias. This is believed to be caused by the surface dangling-bonds (as well as surface states) whose response is controlled by the applied reverse bias. The calculated noise characteristics showed a good agreement with the experimental data. © 2013 SPIE.
Open Access
Passivation of type II InAs / GaSb superlattice photodetectors with atomic layer deposited Al2O3
(SPIE, 2012) Salihoğlu, Ömer; Muti, Abdullah; Kutluer, K.; Tansel, T.; Turan, R.; Kocabaş, Coşkun; Aydınlı, Atilla
We have achieved significant improvement in the electrical performance of the InAs/GaSb midwave infrared photodetector (MWIR) by using atomic layer deposited (ALD) aluminium oxide (Al2O3) as a passivation layer. Plasma free and low operation temperature with uniform coating of ALD technique leads to a conformal and defect free coverage on the side walls. This conformal coverage of rough surfaces also satisfies dangling bonds more efficiently while eliminating metal oxides in a self cleaning process of the Al2O3 layer. Al2O3 passivated and unpassivated diodes were compared for their electrical and optical performances. For passivated diodes the dark current density was improved by an order of magnitude at 77 K. The zero bias responsivity and detectivity was 1.33 A/W and 1.9 x 1013 Jones, respectively at 4 µm and 77 K. Quantum efficiency (QE) was determined as %41 for these detectors.
Open Access
Skin-like self-assembled monolayers on InAs / GaSb superlattice photodetectors
(IOP Institute of Physics Publishing, 2012) Salihoglu, O.; Muti, A.; Kutluer, K.; Tansel, T.; Turan, R.; Aydınlı, Atilla
We report on the effects of monolayer (ML) thick skin-like octadecanethiol (ODT, CH 3[CH 2] 17SH) on type-II InAs/GaSb MWIR photodetectors. Circumventing the ageing effects of conventional sulfur compounds, we use ODT, a self-assembling, long molecular chain headed with a sulfur atom. Photodiodes coated with and without the self-assembled monolayer (SAM) ODT were compared for their electrical and optical performances. For ODT-coated diodes, the dark current density was improved by two orders of magnitude at 77K under 100mV bias. The zero bias responsivity and detectivity were 1.04AW 1 and 2.15 × 10 13 Jones, respectively, at 4μm and 77K. The quantum efficiency was determined to be 37% for a cutoff wavelength of 5.1μm.
Open Access
Thiol passivation of MWIR Type II superlattice photodetectors
(SPIE, 2013) Salihoğlu, Ömer; Muti, Abdullah; Aydınlı, Atilla
Poor passivation on photodetectors can result in catastrophic failure of the device. Abrupt termination of mesa side walls during pixel definition generates dangling bonds that lead to inversion layers and surface traps leading to surface leakage currents that short circuit diode action. Good passivation, therefore, is critical in the fabrication of high performance devices. Silicondioxide has been the main stay of passivation for commercial photodetectors, deposited at high temperatures and high RF powers using plasma deposition techniques. In photodetectors based on III-V compounds, sulphur passivation has been shown to replace oxygen and saturate the dangling bonds. Despite its effectiveness, it degrades over time. More effort is required to create passivation layers which eliminate surface leakage current. In this work, we propose the use of sulphur based octadecanethiol (ODT), CH3(CH2)17SH, as a passivation layer for the InAs/GaSb superlattice photodetectors that acts as a self assembled monolayer (SAM). ODT SAMs consist of a chain of 18 carbon atoms with a sulphur atom at its head. ODT Thiol coating is a simple process that consist of dipping the sample into the solution for a prescribed time. Excellent electrical performance of diodes tested confirm the effectiveness of the sulphur head stabilized by the intermolecular interaction due to van der Walls forces between the long chains of ODT SAM which results in highly stable ultrathin hydrocarbon layers without long term degradation. © 2013 SPIE.