The variations in the responsivity, minority carrier lifetime and shunt resistance (arising due to surface accumulation) have been measured as a function of the gate potential in a HgCdTe gated photoconductor test structure. The measured... more
The variations in the responsivity, minority carrier lifetime and shunt resistance (arising due to surface accumulation) have been measured as a function of the gate potential in a HgCdTe gated photoconductor test structure. The measured variations have been shown ...
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We demonstrate the room temperature deposition of vanadium oxide thin films by pulsed laser deposition (PLD) technique for application as the thermal sensing layer in uncooled infrared (IR) detectors. The films exhibit temperature... more
We demonstrate the room temperature deposition of vanadium oxide thin films by pulsed laser deposition (PLD) technique for application as the thermal sensing layer in uncooled infrared (IR) detectors. The films exhibit temperature coefficient of resistance (TCR) of 2.8%/K implies promising application in uncooled IR detectors. A 2-D array of 10-element test microbolometer is fabricated without thermal isolation structure. The IR response of the microbolometer is measured in the spectral range 8–13 μm. The detectivity and the responsivity are determined as ∼6×105 cm Hz1/2/W and 36 V/W, respectively, at 10 Hz of the chopper frequency with 50 μA bias current for a thermal conductance G∼10–3 W/K between the thermal sensing layer and the substrate. By extrapolating with the data of a typical thermally isolated microbolometer (G∼10−7 W/K), the projected responsivity is found to be around 104 V/W, which well compares with the reported values.
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Vanadium oxide thin films are the potential candidates for uncooled microbolometers due to their high temperature coefficient of resistance (TCR) at room temperature. A 2D array of 10-element test microbolometer without air-gap thermal... more
Vanadium oxide thin films are the potential candidates for uncooled microbolometers due to their high temperature coefficient of resistance (TCR) at room temperature. A 2D array of 10-element test microbolometer without air-gap thermal isolation structure was fabricated with pulsed laser deposited vanadium oxide as IR sensing layer for the first time. Infrared responsivity of the uncooled microbolometer was evaluated in the spectral region 8-15 μm. The device exhibits responsivity of about 12 V/W at 30 Hz chopper frequency for 20 μA bias current. Thermal time constant (τ), Thermal conductance (G) and thermal capacitance (C) are the thermal parameters characterize the performance of the uncooled microbolometer infrared detectors are determined as 15 ms, ∼10-3 W/K and ∼3.5 × 10-5 J/K respectively. The influence of the thermal parameters on the performance of the microbolometer is discussed.
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Abstract The effect of a doped layer on the surface of a mercury cadmium telluride photoconductive detector has been investigated theoretically as a function of the ratio of electrically active carriers in the doped layer to that in the... more
Abstract The effect of a doped layer on the surface of a mercury cadmium telluride photoconductive detector has been investigated theoretically as a function of the ratio of electrically active carriers in the doped layer to that in the base material. It is concluded ...
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The electrical effects of dislocations has been studied by modeling zero-bias resistance-area product (R0A) of long wavelength infrared diodes fabricated in molecular beam epitaxy (MBE)-grown HgCdTe-Si epitaxial films. Results show that... more
The electrical effects of dislocations has been studied by modeling zero-bias resistance-area product (R0A) of long wavelength infrared diodes fabricated in molecular beam epitaxy (MBE)-grown HgCdTe-Si epitaxial films. Results show that dislocations influence both 40 K and 78 K R0A products in high dislocation density (HgCdTe/Si) material. In low dislocation density samples (HgCdTe/CdZnTe), the variations in 78 K R0A are limited by the composition (x) variations in Hg1-xCdxTe material, whereas dislocation contribution dominates the variations at 40 K. The origin of relatively large spread in 40 K R0A in both types of samples is traced to the statistical variations in the core charges of dislocations. It is concluded that additional alternatives besides the reduction of dislocation density (such as control of core charges), may also need attention in order to make Si a viable substrate material for the growth of HgCdTe epitaxial layers suitable for devices operating at 40 K.
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This paper proposes a development of n-on-p structures for realizing very long wavelength infrared (VLWIR) detector arrays on mercury cadmium telluride (HgCdTe) epitaxial layers grown on Si substrates. It is shown from a comparative study... more
This paper proposes a development of n-on-p structures for realizing very long wavelength infrared (VLWIR) detector arrays on mercury cadmium telluride (HgCdTe) epitaxial layers grown on Si substrates. It is shown from a comparative study of zero-bias resistance-area product (R0A) of diodes in n-on-p and p-on-n configurations that the n-on-p structure has promising potential to control contribution of dislocations, without actually reducing dislocation density below the current level (mid-106 cm−2) of HgCdTe/Si material technology. The resulting gain will be in terms of both higher numerical magnitudes of R0A and its reduced scatter.
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A study of the contribution of dislocations to the zero-bias resistance–area product (R0A) of long-wavelength infrared n-on-p mercury cadmium telluride (HgCdTe) diodes has been carried out from the modelling of the temperature dependence... more
A study of the contribution of dislocations to the zero-bias resistance–area product (R0A) of long-wavelength infrared n-on-p mercury cadmium telluride (HgCdTe) diodes has been carried out from the modelling of the temperature dependence of R0A product of diodes fabricated in a material of known dislocation density. The capture probabilities of electrons and holes relevant to the modelling of the effect of dislocations in p-type HgCdTe have been thus evaluated. The general applicability of these parameters has been further verified by using them to model the temperature variation of the R0A of the diodes reported by other groups. Results of the present study show that dislocations degrade the impedance of HgCdTe diodes at low temperatures on account of their shunt-resistance behavior rather than the commonly accepted dislocation-assisted tunnelling mechanism. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)
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This paper reports the possibility of assessing the relative surface and bulk contributions in HgCdTe junction diodes by analyzing the Current - voltage (I - V) and dynamic impedance - voltage (Rd - V) characteristics of an individual... more
This paper reports the possibility of assessing the relative surface and bulk contributions in HgCdTe junction diodes by analyzing the Current - voltage (I - V) and dynamic impedance - voltage (Rd - V) characteristics of an individual diode. As an example, an analysis of the experimental data obtained on diodes fabricated in our laboratory on bulk grown p-type HgCdTe wafers using B+ implantation and ZnS passivating layers will be presented.
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This paper proposes a theoretical model to calculate the ohmic shunt resistance in mercury cadmium telluride junction diodes. It is shown that the observed temperature dependence of the shunt resistance of the mercury cadmium telluride... more
This paper proposes a theoretical model to calculate the ohmic shunt resistance in mercury cadmium telluride junction diodes. It is shown that the observed temperature dependence of the shunt resistance of the mercury cadmium telluride diodes could be well accounted for with the proposed model. The two known sources of ohmic current namely surface effects and dislocations have been discussed while calculating the shunt resistance.
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Contribution of dislocations to 1/f noise has been investigated by analysing the temperature dependence of the noise, dark current and zero-bias resistance–area product of mercury cadmium telluride (HgCdTe) diodes. It is shown that... more
Contribution of dislocations to 1/f noise has been investigated by analysing the temperature dependence of the noise, dark current and zero-bias resistance–area product of mercury cadmium telluride (HgCdTe) diodes. It is shown that irrespective of the type of diode, i.e. n-on-p or p-on-n, dislocation contribution to 1/f noise can be described by in = 1 × 10−2Ish and in = 6 × 10−4Ish for planar and mesa configurations respectively, where, Ish is the current conducted through the dislocations in the base of the diode. A physical model, consistent with the shunt resistance behaviour of dislocations, has been proposed to understand the role of dislocations in enhancing 1/f noise of these diodes.
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Guided by the simple physical and geometrical considerations, an analytical approach is presented to model a junction diode in a two-dimensional array. The proposed model includes the contributions of the lateral diffusion current and the... more
Guided by the simple physical and geometrical considerations, an analytical approach is presented to model a junction diode in a two-dimensional array. The proposed model includes the contributions of the lateral diffusion current and the surface leakage current ...
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Abstract IR transmission curves of Hg 1− x Cd x Te (0.2< x< 0.3) epilayers on IR transparent substrates have been simulated on computer using a recently published model.[J. appl. Phys. 66, 3763 (1989)]. Using the computer simulated... more
Abstract IR transmission curves of Hg 1− x Cd x Te (0.2< x< 0.3) epilayers on IR transparent substrates have been simulated on computer using a recently published model.[J. appl. Phys. 66, 3763 (1989)]. Using the computer simulated data, the frequency of the 50% ...
