Temperature Dependent Spectral Response Research Articles

Temperature-dependent spectral response mechanism in GaAs-based blocked-impurity-band (BIB) far-infrared detectors

Temperature-dependent spectral response mechanism in GaAs-based blocked-impurity-band (BIB) far-infrared detectors has been investigated. Device structure, processing steps and physical models are described in detail. In this work, our discussion is mainly focused on the operation temperature (Tope) of BIB detector. It is demonstrated that the critical Tope and the optimal Tope both exist for GaAs-based BIB detector. It is only when the temperature-assisted photo electron excitation process is fundamentally equivalent to the temperature-assisted photo electron recombination process that the optimal Tope occurs, and it is only when the temperature-assisted photo electron excitation process is dominated by the temperature-assisted photo electron recombination process that the critical Tope occurs.

Accuracy of activation energy from Arrhenius plots and temperature-dependent internal photoemission spectroscopy

In this work, the activation energy obtained from the temperature dependent internal photoemission spectroscopy (TDIPS) and thermionic dark currents using GaAs/AlGaAs photodetectors are compared. Different barrier heights within the p-type GaAs/AlGaAs heterostructures are studied. The temperature dependent spectral response shows the red-shifting of the detector threshold wavelength for increasing temperature due to the decreasing band-offset. The activation energy extracted from Arrhenius plot of the dark current-voltage-temperature (I-V-T), and measured spectral response show the carrier activation energy increases with increasing Al mole fraction and decreases with increasing doping density. For Infrared detectors with ≤6.5 μm, the Arrhenius analysis yields the values of activation energy with less than 5% deviation from the actual or TDIPS fitting values. However, for detectors with longer threshold wavelengths (≫9.3 μm), activation energy extracted from the Arrhenius plot leads to energy values which deviate more than ~10% from the corresponding TDIPS values. The higher percentage deviation (≫10%) of activation energy determined by Arrhenius plot from the corresponding TDIPS values attribute to the temperature dependent Fermi distribution tailing effect and Fowler–Nordheim tunneling current.

Photo-response edge effect of back-illuminated planar InGaAs/InP focal plane arrays

Based on planer process with sealed-ampoule diffusion method, back-illuminated 32 × 32 pixels planar InGaAs/InP detectors were fabricated by using N-InP/i-In0.53Ga0.47As/N-InP double-heterostructure epitaxial materials and wire-bonded to readout integrated circuit (ROIC) to form near infrared focal plane arrays (FPAs). The photo-response edge effect of the detector was further analyzed with the aid of laser beam induced current (LBIC) technique under different laser powers. Moreover, the photoelectric characteristics including I-V characteristics and temperature-dependent spectral response were also investigated. The results indicate that the photo-response edge effect is caused by the lateral collection effect of photogenerated carriers, so the edge pixels could absorb more carriers generated in the surrounding undoped Zn-diffused regions. And then the method to optimize the detector design and performance was given. Otherwise, the main component of the forward current is diffusion current at room temperature. The density of dark current and R0A are 7.4 nA cm−2 (@−100 mV) and 4.7 × 106 Ωcm2 respectively. The average peak detectivity is 1.0 × 1012 cm Hz1/2/W.

Temperature-dependent spectral response of arc-induced long-period fiber gratings accompanied with acrylic coating

Temperature-dependent spectral response of arc-induced long-period fiber gratings accompanied with acrylic coating

Effects of material parameters on the temperature dependent spectral response of In0.83Ga0.17As photodetectors

The effects of material parameters on the temperature dependent features of the spectral response of wavelength extended In0.83Ga0.17As photodetector have been investigated both experimentally and theoretically. The decline of the responsivity with drop of temperature has been observed using Fourier transformed infrared spectroscopy. Adopting a simple but clear analytical model, the material and structural parameters of the photodetector were connected with the temperature dependent characteristics of responsivity effectively; the main temperature dependent parameters have been analyzed and taken into account by using simulation method. Results show that the temperature dependent diffusion length of the minority carriers in absorption layer plays the most important role on the distinct positive temperature coefficient of responsivity. Our calculation results also suggest that the enhanced minority carrier diffusion length and depletion width could readily restrain the temperature effects of the responsivity and thus improve the device performance.

Temperature dependent spectral response and detectivity of GeSn photoconductors on silicon for short wave infrared detection.

The GeSn direct gap material system, with Si complementary-metal-oxide semiconductor (CMOS) compatibility, presents a promising solution for direct incorporation of focal plane arrays with short wave infrared detection on Si. A temperature dependence study of GeSn photoconductors with 0.9, 3.2, and 7.0% Sn was conducted using both electrical and optical characterizations from 300 to 77 K. The GeSn layers were grown on Si substrates using a commercially available chemical vapor deposition reactor in a Si CMOS compatible process. Carrier activation energies due to ionization and trap states are extracted from the temperature dependent dark I-V characteristics. The temperature dependent spectral response of each photoconductor was measured, and a maximum long wavelength response to 2.1 μm was observed for the 7.0% Sn sample. The DC responsivity measured at 1.55 μm showed around two orders of magnitude improvement at reduced temperatures for all samples compared to room temperature measurements. The noise current and temperature dependent specific detectivity (D*) were also measured for each sample at 1.55 μm, and a maximum D* value of 1 × 10(9) cm·√Hz/W was observed at 77 K.

Temperature dependent spectral response characteristic of III-V compound tandem cell

The GaInP/GaAs/Ge triple-junction tandem cells with a conversion efficiency of 27.1% were fabricated using metalorganic chemical vapor deposition (MOCVD) technique. Temperature dependence of the spectral response measurements of the GaInP/GaAs/Ge tandem cell was performed by a quantum efficiency system at temperatures ranging from 25°C to 160°C. The red-shift phenomena of the absorption limit for all subcells were observed with increasing temperature, which is dued to the energy gap narrowing with temperature. The short-circuit current densities (J sc) of GaInP, GaAs and Ge subcells at room temperature calculated based on the spectral response data were 12.9, 13.7 and 17 mA/cm2, respectively. The temperature coefficient of J sc for the tandem cell was determined to be 8.9 μA/(cm2 · °C), and the corresponding temperature coefficient of the open-circuit voltage deduced from the series-connected model was −6.27 mV/°C.

Electrical and optical characteristics of two color mid wave HgCdTe infrared detectors

Two-color mid wave triple-layer heterojunction HgCdTe detectors were studied using temperature-dependent current–voltage (I–V) measurements, temperature-dependent spectral response measurements, and temperature-dependent noise measurements. The reverse biased dark current shows diffusion-limited behavior for T>125 K. The same data show evidence for generation-recombination-type behavior for the longer wavelength junction at temperatures between 100 and 125 K. For temperatures less than 100 K, the measurements are background limited by photon flux, even though these measurements are performed at nominal zero background. The upper junction shows soft reverse breakdown voltages on the order of about 250 mV, while the bottom junction shows no breakdown for V<500 mV. At 80 K, the R0A product is in excess of 1×106 Ω cm2. In forward bias, the current–voltage characteristics of the lower junction are diffusion limited for all temperatures, while at lower temperatures, the upper junction showed generation-recombination behavior. Optical measurements found a cutoff wavelength of about 4 μm for the lower junction and about 4.5 μm for the upper junction. The spectral crosstalk was less than 3%. At 80 K, the frequency-dependent noise of the shorter wavelength junction showed no dependence on bias, while for the longer wavelength junction, the noise at lower frequencies increased with bias. There is no difference in the noise characteristics when either the photon flux or the temperature is increased.

Spectral characteristics of [formula omitted] heterostructures

We have examined the current-voltage characteristic of i-a-Si:H n-c-Si heterojunction Schottky solar cells in the dark and under different illumination (spectrum AM 1.5) intensities as well as the voltage- and temperature-dependent spectral response of these devices. The photo-current from the crystalline silicon depends on both voltage and temperature due to their influence on the impact of the band offsets. From our measurements of the spectral response we conclude that there is a small conduction band offset ΔE c and a large valence band offset ΔE v at the i-a-Si:H n-c-Si heterojunction. The large valence band offset inhibits the collection of photogenerated holes from the crystalline silicon under normal photovoltaic conditions. Thus, the current-voltage characteristic under illumination between V = 0 V and V = V oc is caused only by the photocurrent from the a-Si:H layer.

Solar collector development : Heath, Atwood R., Jr., and Preston T. Maxwell, NASA, Astronautics and Aerospace Engineering, May 1963, 4 pp., Illus.

We have examined the current-voltage characteristic of i-a-Si:Hn-c-Si heterojunction Schottky solar cells in the dark and under different illumination (spectrum AM 1.5) intensities as well as the voltage- and temperature-dependent spectral response of these devices. The photo-current from the crystalline silicon depends on both voltage and temperature due to their influence on the impact of the band offsets. From our measurements of the spectral response we conclude that there is a small conduction band offset ΔEc and a large valence band offset ΔEv at the i-a-Si:Hn-c-Si heterojunction. The large valence band offset inhibits the collection of photogenerated holes from the crystalline silicon under normal photovoltaic conditions. Thus, the current-voltage characteristic under illumination between V = 0 V and V = Voc is caused only by the photocurrent from the a-Si:H layer.