Jarek Antoszewski

Third-generation infrared photodetector arrays

Hitherto, two distinct families of multielement detector arrays have been used for infrared (IR) imaging system applications: linear arrays for scanning systems (first generation) and two-dimensional arrays for staring systems (second generation). Nowadays, third-generation IR systems are being developed which, in the common understanding, provide enhanced capabilities such as larger numbers of pixels, higher frame rates, better thermal resolution, multicolor functionality, and/or other on-chip signal-processing functions. In this paper, fundamental and technological issues associated with the development and exploitation of third-generation IR photon detectors are discussed. In this class of detectors the two main competitors, HgCdTe photodiodes and quantum-well photoconductors, are considered. This is followed by discussions focused on the most recently developed focal plane arrays based on type-II strained-layer superlattices and quantum dot IR photodetectors. The main challenges facing multicolor devi...

Improved quantitative mobility spectrum analysis for Hall characterization

We present an improved quantitative mobility spectrum analysis (i-QMSA) procedure for determining free electron and hole densities and mobilities from magnetic-field-dependent Hall and resistivity measurements on bulk or layered semiconductor samples. The i-QMSA technique is based on a fundamentally new approach, which optimizes the fit to the conductivity tensor components and their slopes by making those adjustments in the mobility spectra that result in the greatest error reduction. Empirical procedures for manipulating the mobility spectra are also introduced, with the dual purpose of reducing the error of the fit and simplifying the shape of the spectra to minimize the presence of unphysical artifacts. A fully automated computer implementation of the improved QMSA is applied to representative synthetic and real data sets involving various semiconductor material systems. These results show that, as compared with previous approaches, the presented algorithm maximizes the information that may be extract...

New concepts in infrared photodetector designs

In 1959, Lawson and co-workers published the paper which triggered development of variable band gap Hg1−xCdxTe (HgCdTe) alloys providing an unprecedented degree of freedom in infrared detector design. HgCdTe ternary alloy has been used for realization of detectors operating under various modalities including: photoconductor, photodiode, and metal-insulator-semiconductor detector designs. Over the last five decades, this material system has successfully overcome the challenges from other material systems. It is important to notice that none of these competitors can compete in terms of fundamental properties. The competition may represent more mature technology but not higher performance or, with the exception of thermal detectors, higher operating temperatures (HOTs) for ultimate performance. In the last two decades, several new concepts for improvement of the performance of photodetectors have been proposed. These new concepts are particularly addressing the drive towards the so called HOT detectors aiming to increase detector operating temperatures. In this paper, new strategies in photodetector designs are reviewed, including barrier detectors, unipolar barrier photodiodes, multistage detectors and trapping detectors. Some of these new solutions have emerged as a real competitor to HgCdTe photodetectors.

MAGNETIC FIELD DEPENDENT HALL DATA ANALYSIS OF ELECTRON TRANSPORT IN MODULATION-DOPED ALGAN/GAN HETEROSTRUCTURES

Experimental magnetic field dependent Hall and resistivity data is presented for two modulation-doped AlGaN/GaN heterostructures in the temperature range from 6 to 300 K and for a magnetic field up to 12 T. The mobility and concentration of electrons within the two-dimensional electron gas (2DEG) at the AlGaN/GaN interface and within the underlying GaN layer are readily separated and characterized using quantitative mobility spectrum analysis. The observed transport parameters of the 2DEG are explained using the classical band theory for a degenerate electron gas. Analysis of the temperature dependencies of mobility and electron concentration in the GaN layer and 2DEG indicates that electron transport in the GaN layer is dominated by carriers in the conduction band for the case of low-doping ( 1018 cm−3). The simultaneous analysis of the multilayer AlGaN/GaN structure applied in this work renders the results applicable directly...

Generation-recombination effects on dark currents in CdTe-passivated midwave infrared HgCdTe photodiodes

The effect of an abrupt CdTe∕HgCdTe passivation heterointerface on generation recombination and dark currents in n-on-p midwave infrared photodiodes with 5.2-μm cut-off wavelength has been investigated. Experimentally, it was observed that the zero-bias-dynamic resistance, R0, at low temperatures scales with the perimeter of the n-on-p junction, rather than with the junction area, suggesting that surface effects are dominant. The diode current–voltage characteristics at low temperatures indicate significant contributions from tunneling effects, which is the dominant leakage current mechanism for reverse bias greater than approximately 30mV. These two observations suggest that the region where the junction terminates at the CdTe∕HgCdTe abrupt interface is responsible for the above effects. A two-dimensional model has been developed to investigate the dark current mechanisms in the vicinity of the junction termination at CdTe∕HgCdTe interface, which also takes into account the effect of dislocations on gene...

Progress, challenges, and opportunities for HgCdTe infrared materials and detectors

This article presents a review on the current status, challenges, and potential future development opportunities for HgCdTe infrared materials and detector technology. A brief history of HgCdTe infrared technology is firstly summarized and discussed, leading to the conclusion that HgCdTe-based infrared detectors will continue to be a core infrared technology with expanded capabilities in the future due to a unique combination of its favourable properties. Recent progress and the current status of HgCdTe infrared technology are reviewed, including material growth, device architecture, device processing, surface passivation, and focal plane array applications. The further development of infrared applications requires that future infrared detectors have the features of lower cost, smaller pixel size, larger array format size, higher operating temperature, and multi-band detection, which presents a number of serious challenges to current HgCdTe-based infrared technology. The primary challenges include well co...

Stress in low-temperature plasma enhanced chemical vapour deposited silicon nitride thin films

Two experimental techniques have been investigated to examine residual stress in low-temperature plasma enhanced chemical vapour deposited (PECVD) SiNx thin films: one that measures the stress-induced substrate curvature, and the other that takes advantage of the stress-induced deformation of freestanding diagnostic microstructures. A general linear dependence of residual stress on SiNx deposition temperature is observed, with the magnitude of stress changing linearly from ~300 MPa tensile stress to ~600 MPa compressive stress as the deposition temperature is decreased from 300 to 100 °C. However, the results deviate from the linear dependence by a different degree for both measurement techniques at low deposition temperatures. The stress values obtained via the substrate curvature method deviate from the linear dependence for deposition temperatures below 200 °C, whereas the values obtained via the diagnostic microstructures method deviate from the linear dependence for deposition temperatures below 100 °C. Stress uniformity over the deposition area is also investigated.

p-to-n type-conversion mechanisms for HgCdTe exposed to H2/CH4 plasmas

The role of hydrogen incorporation in H2/CH4 reactive ion etching (RIE) induced type-conversion of p-type HgCdTe is investigated. A model is proposed in which hydrogen is incorporated into the HgCdTe crystal lattice in at least three different forms. It is proposed that the junction formation mechanism is a mixture of RIE-induced damage and Hg interstitial formation to which hydrogen forms strong bonds, and hydrogen-induced neutralization of acceptors. Confirmation of the model is presented based on experimental secondary ion mass spectroscopy of RIE-induced junctions, transport measurements reported previously, and initial diode bake stability testing.

Mercury-cadmium-telluride waveguides - A novel strategy for on-chip mid-infrared sensors

We report the first planar waveguides made from mercury-cadmium-telluride (MCT)-a material to date exclusively used for mid-infrared (MIR) detector elements-serving as on-chip MIR evanescent field transducers in combination with tunable quantum cascade lasers (tQCLs) emitting in the spectral regime of 5.78-6.35 μm. This novel MIR sensing approach utilizes structured MCT chips fabricated via molecular beam epitaxy (MBE) as waveguide enabling sensing via evanescent field absorption spectroscopy, as demonstrated by the detection of 1 nL of acetone. Complementary finite difference time domain (FDTD) simulations fit well with the experimentally obtained data and predict an improvement of the limit of detection by at least 2 orders of magnitude upon implementation of thinner MCT waveguides. With the first demonstration of chemical sensing using on-chip MCT waveguides, monolithically fabricated IR sensing systems directly interfacing the waveguide with the MCT detector element may be envisaged.

Analysis of magnetic field dependent Hall data in narrow bandgap Hg1−xCdxTe grown by molecular beam epitaxy

The analysis of magnetic field dependent Hall data is presented for three representative Hg1−xCdxTe layers grown by Molecular Beam Epitaxy with x in the range 0.193 to 0.244. These samples exhibit ‘‘anomalous’’ Hall characteristics which are analyzed using a hybrid approach consisting of mobility spectrum (MS) analysis followed by a multi‐carrier fitting (MCF) procedure. This hybrid approach is able to readily separate contributions to the total conductivity arising from extrinsic carriers, thermally activated intrinsic electrons, and two‐dimensional electron layers. The extracted transport parameters for thermally activated intrinsic electrons are shown to be in excellent agreement with established physical models for narrow bandgap HgCdTe. The two‐dimensional electron layers are found to be only weekly temperature dependent with an electron mobility in the range of 2 to 4×104 cm2/V s and a sheet density in the range of 1011 to 1012 cm−2. Of particular interest, is the fact that the ‘‘anomalous’’ Hall ch...