Superlattice Photodetectors Research Articles

Strain engineered < Si/Si0.97C0.03 > superlattice photodetector for optoelectronic applications: a comprehensive numerical analysis and experimental verification

Strain engineered < Si/Si0.97C0.03 > superlattice photodetector for optoelectronic applications: a comprehensive numerical analysis and experimental verification

Comparison of type II superlattice InAs/InAsSb barrier detectors operating in the mid-wave infrared range

Four types of barrier detectors based on a type II InAs/InAsSb superlattice with a wide-gap barrier made of a solid AlInAsSb lattice matched to the GaSb buffer were compared. The tested detectors differed in the type of doping of the active layer and the level and type of doping of the contact layer at the barrier. The epitaxial layers were deposited on GaAs (100) substrates using the molecular beam epitaxy method. The spectral and current–voltage characteristics of the analyzed detectors were compared. The highest current responsivities were observed in the structure with a p-type absorber (p+BpN+). Detectors with an n-type absorber (p+Bnn+, n+Bnn+, and nBnn+) show an increase in the current responsivity with an increase in the reverse bias voltage due to the reduction in the undesirable barrier in the valence band. Arrhenius characteristics for the dark current show that only in nBnn+ detectors, it was possible to limit the generation–recombination current. These detectors at 150 K were characterized by the highest normalized detectivity of approximately 3 × 1011 cm · Hz1/2/W. The obtained results were compared with literature data, showing that the parameters of type II superlattice photodetectors are close to those of HgCdTe photodiodes according to the “Rule 07” and “Rule 22” principles.

Design and calculation of photoelectric properties of resonance enhanced InAs/GaSb type-II superlattices photodetectors with diffraction rings structure

The resonance enhanced InAs/GaSb type-II Superlattices (T2SLs) infrared detectors with diffraction rings is designed, and the photoelectric characteristics are calculated and studied in this paper. The diffraction rings are designed on the top surface of T2SLs detector to control the incident light inside the device by forming the resonant cavity. We designed the structure of the conventional PIN InAs/GaSb T2SLs photodetector, calculated the energy band structure of the absorption layer, and analyzed the influence of the thickness of the absorption layer on the photoelectric performance. It is proved that blindly increasing the thickness of the absorption layer cannot effectively improve the device performance. We further studied the quantum efficiency (QE) and electric field distribution of the device after adding the diffraction ring structure. The results show that the structure with diffraction rings can significantly improve the QE of the photodetector without increasing the dark current. The interaction between the diffraction ring and the metal contact layer will enhance the localization of the electric field and further increase the light absorption between the semiconductor layers.

Hybrid Signal Processing for Automatic Detection and Removal of Material Absorption and Noise From Microsphere-Lens-Enhanced Midwave Infrared Type II Strained Layer Superlattice Photodetectors

Hybrid Signal Processing for Automatic Detection and Removal of Material Absorption and Noise From Microsphere-Lens-Enhanced Midwave Infrared Type II Strained Layer Superlattice Photodetectors

Simulational investigation of self-aligned bilayer linear grating enabling highly enhanced responsivity of MWIR InAs/GaSb type-II superlattice (T2SL) photodetector

Linear gratings polarizers provide remarkable potential to customize the polarization properties and tailor device functionality via dimensional tuning of configurations. Here, we extensively investigate the polarization properties of single- and double-layer linear grating, mainly focusing on self-aligned bilayer linear grating (SABLG), serving as a wire grid polarizer in the mid-wavelength infrared (MWIR) region. Computational analyses revealed the polarization properties of SABLG, highlighting enhancement in TM transmission and reduction in TE transmission compared to single-layer linear gratings (SLG) due to optical cavity effects. As a result, the extinction ratio is enhanced by approximately 2724-fold in wavelength 3–6 μm. Furthermore, integrating the specially designed SABLG with an MWIR InAs/GaSb Type-II Superlattice (T2SL) photodetector yields a significantly enhanced spectral responsivity. The TM-spectral responsivity of SABLG is enhanced by around twofold than the bare device. The simulation methodology and analytical analysis presented herein provide a versatile route for designing optimized polarimetric structures integrated into infrared imaging devices, offering superior capabilities to resolve linear polarization signatures.

Low dark current density extended short-wavelength infrared superlattice photodetector with atomic layer deposited Al2O3 passivation.

We report on a low dark current density P-B-i-N extended short-wavelength infrared photodetector with atomic layer deposited (ALD) A l 2 O 3 passivation based on a InAs/GaSb/AlSb superlattice. The dark current density of the A l 2 O 3 passivated device was reduced by 38% compared to the unpassivated device. The cutoff wavelength of the photodetector is 1.8µm at 300K. The photodetector exhibited a room-temperature (300K) peak responsivity of 0.44A/W at 1.52µm, corresponding to a quantum efficiency of 35.8%. The photodetector exhibited a specific detectivity (D ∗) of 1.08×1011 c m⋅H z 1/2/W with a low dark current density of 3.4×10-5 A/c m 2 under -50m v bias at 300K. The low dark current density A l 2 O 3 passivated device is expected to be used in the fabrication of extended short-wavelength infrared focal plane arrays for imaging.

Irradiation Temperature Influence on the Degradation of the Electrical Performances of Midwave Infrared Type-II Superlattice Detectors

In this work, we present the influence of the irradiation temperature on electrical characterization of MidWave infrared (MWIR) InAs/GaSb type-II superlattice (T2SL) photodetector, showing cut-off wavelength equal to 5μm at 90K. The proton irradiations were performed with 60 MeV protons and fluences up to 8x10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">11</sup> H <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">+</sup> /cm² at cryogenic (100K) or room temperature (300K). The gamma irradiation, from a Cobalt-60 source, allows to reach a dose up to 50 krad(Si). We observed that degradation of the dark current under proton or gamma irradiations is strongly dependent on the temperature of the detector during irradiation but also on the protection layer used during the detector’s technological process.

Mid-Wavelength InAs/InAsSb Superlattice Photodetector With Background Limited Performance Temperature Higher Than 160 K

We report on a mid-wavelength (MW) type II superlattice (T2SL) photodetector using Ga-free InAs/InAsSb SL structure. X-ray diffraction (XRD) measurements indicate that the strained SL material is of very high quality. It is demonstrated that the background limited performance (BLIP) temperature of the detector is above 160 K and the dark current is dominated by the diffusion mechanism when temperature is above 160 K. At 77, 160, and 280 K, the 50% cutoff wavelength of the detector is 4.54, 4.89, and 5.56 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mu \text{m}$ </tex-math></inline-formula> , respectively. The responsivity at the peak wavelength is 2.13 A/W at 77 K and is 2.16 A/W at 160 K. We also extract the Varshni parameters of the SL structure. The results indicate that the Ga-free SL structure is similar to InAs bulk material in terms of the Varshni parameters.

Quasi-three-dimensional nanopost array integrated Type-II superlattice photodetectors for infrared multispectral filtering

Angle-insensitive and high-transmission infrared spectral filters, comprising periodic quasi-three-dimensional (quasi-3D) nanopost arrays, are fabricated using a nanoimprint lithography technique and directly integrated onto an InAs/GaSb type-II superlattice (T2SL) photodetector. Simulation results of the plasmonic filters reveal that the transmission peak wavelength is linearly adjusted by tuning the filter period as a result of the propagated and localized surface plasmon resonances of the quasi-3D nanopost array structure. Additionally, the transmission peak wavelength of the array structure is measured to increase with decreasing nanopost height owing to stronger field coupling between the Au hole and disk arrays. A tunable bandpass filtering function of the quasi-3D nanopost-integrated T2SL photodetector is successfully demonstrated with narrow bandwidths in the spectral range of 2–6 μm. Our findings offer a significant potential for a scalable low-cost manufacturing method of compact snapshot multispectral infrared imagers for portable-field imaging or airborne-platform-based imaging applications.

Modeling Infrared Superlattice Photodetectors: From Nonequilibrium Green’s Functions to Quantum-Corrected Drift Diffusion

Carrier transport in type-II superlattice photodetectors is investigated by means of a rigorous nonequilibrium Green's function model based on a physics-based B\"uttiker-probe formalism. Intraband scattering self-energies (carrier-phonon interactions) are computed in the self-consistent Born approximation, while interband self-energies (Shockley-Read-Hall and optical transitions) are included in terms of semiclassical generation-recombination rates, neglecting interband renormalization effects. Current conservation is achieved with an efficient Newton-Raphson algorithm. While carrier transport in infrared detectors is usually understood in terms of quantities (e.g., mobilities and quasi-Fermi-levels) that are admittedly not germane to nonequilibrium Green's function theory, the proposed model provides a quantum-kinetic description of tunneling, miniband transport, hopping, and carrier extraction within a drift-diffusion-friendly framework. The connection with semiclassical theories allows exploration of the possibilities offered by Poisson-Schr\"odinger or localization landscape drift-diffusion approaches.

Quantum efficiency contributions for type-II InAs/GaSb SL photodetectors

Abstract We analyze the quantum efficiency (QE) constituents of three type-II InAs/GaSb superlattice (T2SL) photodetectors with identical period lengths and different i- and p-layer thicknesses. The T2SL mid-wave detectors show the spectral response with 50% cut-off wavelength equal to 4.88 μm at 79 K. Empirical pseudopotential method (EPM) is employed to define band structure such as bandgap energy and heavy hole–light hole (HH–LH) splitting energies. Peak responsivities are measured as 1.14, 1.20, and 1.26 A/W at 4 μm under zero bias, with corresponding QEs of 35%, 37%, and 39%. The QEs of pin detectors are simulated by photocurrent analysis according to the Hovel Model to determine the contribution of QE components.

Effective suppression of surface leakage currents in T2SL photodetectors with deep and vertical mesa sidewalls via TMA and H2 plasma combined pretreatment

For type-II InAs/GaSb superlattice (T2SL) photodetectors with deep and vertical mesa sidewalls, passivation for suppression of surface leakage currents is facing two key challenges that in the conformal coating of sharp sidewalls and increasing dominance of surface leakage currents as device dimensions shrink. In this work, atomic layer deposited (ALD)-Al2O3 and SiO2 method was employed as conformal passivation for deep and vertical mesa sidewalls. And a stable and high-quality interface between the ALD-Al2O3 and T2SL mesa sidewalls was obtained by the combined pretreatment of trimethylaluminum (TMA) and H2 plasma exposure (Al2O3TH), and thus a significant improvement in electrical performances has been achieved. The electrical performances before and after baking were compared among the Al2O3TH, conventional sulfur plus SiO2 passivated photodiodes. The dark current density of Al2O3TH passivated photodiodes were improved by 81% at 77 K under 0.1 V reverse bias and exhibited no deterioration after 90 °C-4 days baking treatment. Investigation on the effects of TMA and/or H2 plasma pretreatments demonstrates that combined pretreatment of TMA and H2 plasma, rather than TMA or H2 plasma alone, prior to the deposition of ALD-Al2O3 leads to a more thorough elimination of interface native oxides and surface states introduced in mesa process. The innovative application of this effective surface pretreatment technique is very encouraging for the passivation of deep and vertical sidewalls in III-V compound-based devices, such as large-format T2SL infrared detectors.

Interband optical absorption obtained by pseudopotential method for type-II InAs/GaSb SL photodetectors

We have calculated interband optical absorption for InAs/GaSb based type-II superlattice (SL) structures. The empirical pseudopotential method (EPM) has been used as an alternative to the k.p method since it is less sophisticated while providing similar results in the mid wavelength infrared range and long wavelength infrared range atmospherics bands for comparison. EPM results show that the bandgap wavelengths of SLs have been predicted with the underestimating of 0.4 µm. This corresponds to an uncertainty of less than 0.3 monolayer in the layer width. The theoretical estimation is comparable with the uncertainty of the layer width during the growth process. Heterostructures or SLs with their ternary and quaternary alloys can be calculated by this method to identify electronic and optical parameters for both intersubband and interband applications.

Cross-correlation method for noise measurements of photodetectors used for laser absorption spectroscopy

The paper presents noise measurements of low-resistance photon detectors with a specially developed system. These measurements are significant for many applications. This issue is particularly critical for laser absorption spectroscopy systems to detect trace amounts of gases. In these systems, the detection limit is determined by noise origins, e.g., light source, background, and detector noise and its readout electronics. The use of some specially designed components of the system (low-noise - 3.6 × 10&lt;sub&gt;-19&lt;/sub&gt; V&lt;sub&gt;2&lt;/sub&gt;/Hz for f &gt;1 kHz) cross-correlation signal processing provides to obtain a measuring floor noise below 10&lt;sub&gt;-18&lt;/sub&gt; V&lt;sub&gt;2&lt;/sub&gt;/Hz for f &gt; 10 Hz and below 10&lt;sub&gt;-19&lt;/sub&gt; V&lt;sub&gt;2&lt;/sub&gt;/Hz for f &gt; 1 kHz after ten minutes’ analysis. Measurements of some reference resistors have verified the system’s performance. Finally, the system was also applied to determine the spectral noise density of the II -Type SuperLattice photodetector made of InAs / InAsSb.

Low-Noise Programmable Voltage Source

This paper presents the design and testing of a low-noise programmable voltage source. Such a piece of instrumentation is often required as part of the measurement setup needed to test electronic devices without introducing noise from the power supply (such as photodetectors, resistors or transistors). Although its construction is based on known configurations, here the discussion is focused on the characterization and the minimization of the output noise, especially at very low frequencies. The design relies on a digital-to-analog converter, proper lowpass filters, and a low-noise Junction Field-Effect Transistors (JFET) based voltage follower. Because of the very low level of output noise, in some cases we had to resort to cross-correlation in order to reduce the background noise of the amplifiers used for the characterization of the programmable source. Indeed, when two paralleled IF9030 JFETs are used in the voltage follower, the output noise can be as low as 3 nV/√Hz, 0.6 nV/√Hz and 0.4 nV/√Hz at 1 Hz, 10 Hz and 100 Hz, respectively. The output voltage drift was also characterized and a stability of ±25 µV over 3 h was obtained. In order to better appreciate the performance of the low-noise voltage source that we have designed, its noise performances were compared with those of a set-up based on one of the best low-noise solid-state voltage regulators available on the market. Actual measurements of the current noise in a type-II superlattice photodetector are reported in which the programmable source was used to provide the voltage bias to the device.

The modeling of a SWIR type-II InAs/AlSb superlattice using an ETBM and interface engineering

A short-wavelength infrared InAs/AlSb type-II superlattice photodetector has been modeled with 15 Mono Layer (ML) of InAs and 4 Mono Layer (ML) of AlSb. In this work, the Empirical Tight-Binding Method (ETBM) was used to calculate the band structure and predict the material of the interfaces. In addition, the effective mass of the heavy hole, light hole, and electron was calculated for each type of the interfaces by tight binding s p 3 s ∗ modeling. Based on the results, the material of the interfaces plays a critical role in lattice mismatch and cutoff wavelength. The detector cutoff wavelength can be changed by atomic engineering of the superlattice interfaces and changing the thicknesses of InAs and AlSb. The simulation results are in good agreement with the experimental values and prove that the [ ( I n A s ) 15 − I n S b − ( A l S b ) 4 − A l A s ] is the most suitable structure. In order to match the simulation results with experimental results, the effect of the segregation on the band structure was evaluated. In this case, the cutoff wavelength of the SWIR detector is 3.27 μ m and the lattice mismatch between the superlattice and the GaSb (100) substrate is 0.63%. • A SWIR InAs/AlSb T2SL photodetector has been modeled with 15 ML of InAs and 4 ML of AlSb. • (ETBM) is used to calculate and predict the material of the interfaces. • The effective mass of the heavy hole, light hole, and electron was calculated for each type of the interfaces by tight binding s p 3 s ∗ modeling. • The flowchart of extracting the band structure by ETBM is presented. • The migration of atoms in interfaces is investigated.

High performance Zn-diffused planar mid-wavelength infrared type-II InAs/InAs1−xSbx superlattice photodetector by MOCVD

We report a Zn-diffused planar mid-wavelength infrared photodetector based on type-II InAs/InAs1−xSbx superlattices. Both the superlattice growth and Zn diffusion were performed in a metal-organic chemical vapor deposition system. At 77 K, the photodetector exhibits a peak responsivity of 0.70 A/W at 3.65 μm, corresponding to a quantum efficiency of 24% at zero bias without anti-reflection coating, with a 50% cutoff wavelength of 4.28 μm. With an R0A value of 3.2 × 105 Ω cm2 and a dark current density of 9.6 × 10−8 A/cm2 under an applied bias of −20 mV at 77 K, the photodetector exhibits a specific detectivity of 2.9 × 1012 cm Hz1/2/W. At 150 K, the photodetector exhibits a dark current density of 9.1 × 10−6 A/cm2 and a quantum efficiency of 25%, resulting in a detectivity of 3.4 × 1011 cm Hz1/2/W.

Long Wavelength Type II InAs/GaSb Superlattice Photodetector Using Resonant Tunneling Diode Structure

We report on a long wavelength type-II InAs/GaSb superlattice photodetector using resonant tunneling diode (RTD) structure. The linewidth of the satellite peak of the x-ray diffraction curve of the as-grown sample is only 15.7 arcsec showing a very high structural quality. The response maximum wavelength of the RTD detector is $7.5~\mu \text{m}$ and the 50% cutoff wavelength is $9.6~\mu \text{m}$ at 77 K. The measured QE is 147% at $7.5~\mu \text{m}$ when the applied bias voltage is 1.45 V and the corresponding responsivity is 8.9 A/W. This unusual QE is attributed to a large gain achieved when the device is under a resonant tunneling condition. The corresponding shot noise limited detectivity D* is $1.2\times 10^{10}\text {cm}\cdot \sqrt {Hz}/W$ at 1.45 V at 77 K.

Novel approach to passivation of InAs/GaSb type II superlattice photodetectors

The innovative two-step passivation by octadecanethiol (ODT) self-assembled monolayers (SAMs) and the following silicon dioxide (SiO2) deposition was used for the type-II InAs/GaSb superlattice photodetector. To understand the mechanism of passivation, the (100) GaSb surface covered with the ODT and, for comparison, with the biphenyl thiol (BPT), was characterized by the atomic force microscopy, Raman spectroscopy and contact angle analysis. The results of the study indicated the presence of the homogeneous both the ODT and the BPT monolayers; however, the ODT SAMs were more stable. Therefore, the ODT-based wet treatment was used in the two-step passivation resulting in a reduction of the dark current by one order of magnitude for passivated detector compared with an unpassivated device.

High speed antimony-based superlattice photodetectors transferred on sapphire

We report the substrate transfer of InAs/GaSb/AlSb based type-II superlattice (T2SL) e-SWIR photodetector from native GaSb substrates to low-loss sapphire substrate in order to enhance the frequency response of the device. We have demonstrated the damage-free transfer of T2SL-based thin-films to sapphire substrate using top–down processing and a chemical epilayer release technique. After transfer the −3 dB cut-off frequency increased from 6.4 GHz to 17.2 GHz, for 8 μm diameter circular mesas under −15 V applied bias. We also investigated the cut-off frequency verses applied bias and lateral scaling to assess the limitations for even higher frequency performance.