Electro-physical characteristics of MIS structures with HgTe-based single quantum wells

The paper presents brief research results of the admittance of metal-insulator- semiconductor (MIS) structures based on Hg1-xCdxTe grown by molecular-beam epitaxy (MBE) method including single HgCdTe/HgTe/HgCdTe quantum wells (QW) in the surface layer. The thickness of a quantum well was 5.6 nm, and the composition of barrier layers with the thickness of 35 nm was close to 0.65. Measurements were conducted in the range of temperatures from 8 to 200 K. It is shown that for structure with quantum well based on HgTe capacitance and conductance oscillations in the strong inversion are observed. Also it is assumed these oscillations are related with the recharging of quantum levels in HgTe

Epitaxial 2D PbS Nanoplates Arrays with Highly Efficient Infrared Response

2D nonlayered semiconductors attract intense interest due to their unique planar structure and various fascinating optoelectronic properties. Here, a method is developed to design orientation-controlled and well-defined single-crystalline PbS nanoplates arrays on mica. Furthermore, the single PbS nanoplate device displays great photoresponsivity, detectivity, and photo gain values as high as 1621 A W-1, 1.72 x 10(11) Jones, and 2512, respectively

Extraordinary magnetometry -- a review on extraordinary magnetoresistance

Extraordinary magnetoresistance (EMR) is a geometric magnetoresistance effect occurring in hybrid devices consisting of a high-mobility material joined by a metal. The change in resistance can exceed 107% at room temperature when a magnetic field of 5 T is applied. Magnetic field sensors based on EMR hold the potential formeasuring weak magnetic fields with an unprecedented sensitivity, yet, to date this potential is largely unmet. In this work, we provide an extensive review of the current state-of-the-art in EMR sensors with a focus on the hybrid device geometries, the constituent material properties and applications of EMR. We present a direct comparison of the best devices in literature across magnetoresistance, sensitivity and noise equivalent field for different materials and geometric designs. The compilation of studies collected in this review illustrates the extremely rich possibilities for tuning the magnetoresistive behavior varying the device geometry and material properties. In addition, we aim to improve the understanding of the EMR effect and its interplay with geometry and material properties. Finally, we discuss recent trends in the field and future perspectives for EMR

Bandgap-Engineered HgCdTe Infrared Detector Structures for Reduced Cooling Requirements.

State-of-the-art mercury cadmium telluride (HgCdTe) high performance infrared (IR) p-n heterojunction technology remains limited by intrinsic, thermal Auger generation- recombination (G-R) mechanisms which necessitate strict cooling requirements, and challenges related to processing technology, particularly those associated with achieving stable, controllable in situ p-type doping in molecular beam epitaxy (MBE) grown HgCdTe. These limitations motivate the need to firstly, increase device operating temperatures, and secondly, address material processing issues. This work investigates three alternative HgCdTe IR device architectures as proposed solutions: 1) the high operating temperature (HOT) detector, 2) the nBn detector, and 3) the NBnuN detector. The HOT detector is designed to suppress Auger processes, in turn, reducing the detector noise and cryogenic cooling requirements. A simulation study comparing the device behavior and performance metrics of the Auger-suppressed HOT structure to those obtained for the conventional double layer planar heterostructure (DLPH) device predicts the HOT detector can provide a significant advantage over conventional detectors with an increased operating temperature of ~40-50 K for devices with cutoff wavelengths in the range of 5-12 um. In a related study, a series of experiments is conducted to examine arsenic (As) deep diffusion in HgCdTe with the goal of achieving controllable low p-type doping in the HOT absorber layer to reduce Auger G-R processes by increasing minority carrier lifetimes. Furthermore, a unipolar, barrier-integrated nBn detector structure is proposed to address the challenges associated with p-type doping in MBE grown HgCdTe. Numerically simulated performance characteristics of the HgCdTe nBn device predict values similar to comparable DLPH structures for a range of temperatures, motivating the experimental demonstration of mid- and long-wave IR HgCdTe nBn detectors. Fabricated nBn detectors successfully exhibit barrier-influenced current-voltage and photoresponse characteristics, but are limited by perimeter leakage currents which must be resolved in future work. Finally, this work culminates with the simulation study of the novel, hybrid NBnuN structure which addresses both technology limitations by combining the advantages and designs of the Auger-suppressed HOT and unipolar nBn detectors in a single configuration.Ph.D.Electrical EngineeringUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/91390/1/aitsuno_1.pd

Narrow-gap piezoelectric heterostructure as IR detector

Narrow-gap mercury cadmium telluride thin films grown by MBE and LPE methods onto various substrates (HgCdTe/Si, HgCdTe/GaAs, HgCdTe/CdZnTe) were investigated as a piezoelectric heterostructure for IR detection. The photoresponse, infrared transmittance spectra, parameters of the charge carrier transport, and mechanical properties were studied. Mechanical stresses at the layer-substrate interface were analyzed. HgCdTe-based infrared device is considered, operating in the middle (3–5 μm) infrared spectral range without cryogenic cooling to achieve performance level D* = 2.6 ⋅ 10⁹ ⋅ W⁻¹ cm ⋅Hz¹/² The possibility to detect infrared radiation is thought to be based on the possibility of the spatial separation of the non-equilibrium carriers in the strained semiconductor heterostructure with piezoelectric properties

Physics-based simulation of narrow and wide band gap photonic devices

Historically, infrared (IR) detector technologies are connected mainly with controlling and night-vision problems: in a first stage, applications concerned simply with detection of IR radiation, but very soon capabilities to form IR images were developed, opening the way to systems for recognition and surveillance, especially for military purposes. Since the last decade of the twentieth century, the use of IR imaging systems for civil and peaceful purposes have increased continuously: these include medical and industrial applications, detection of earth resources, earth and universe sciences, etc. As an example, IR imaging is widely used in astronomy, to study interstellar medium and first-stages of stellar evolution; in medicine, IR thermography – IR imaging of the human body – is employed to detect cancers or other trauma; IR detectors are also widely used in automotive industry, chemical process monitoring, global monitoring of environmental pollution and climate changes, etc. The discovery in 1959 by Lawson and co-workers of the wide tunability of the HgCdTe alloy allowed this compound to become one of the most important and versatile materials for detector applications over the entire IR range. A critical contribution to research is given by Technology Computer-Aided Design (TCAD), modeling and simulation. In the first part of this thesis, I present the main part of my research activity, focused on the development of abilities and methodologies for the simulation of realistic three-dimensional HgCdTe-based infrared photodetectors. The purpose is the investigation of generation-recombination (GR) mechanisms and modeling of spectral photoresponse in narrow-gap HgCdTe-based photodetectors, with one-, two and three-dimensional (1D, 2D, 3D) realistic TCAD models (Chapters 1-5). Another important topic of industrial research in semiconductor physics deals with nitride-based light-emitting diodes (LEDs). From automotive to streetlights, from lights in our houses to the displays of TVs and smartphones, LED-based technology is making its way in the market. This proliferation would have been impossible without GaN-based LEDs, whose invention by Isamu Akasaki, Hiroshi Amano and Shuji Nakamura has been rewarded with the 2014 Nobel Prize in Physics. Nevertheless, GaN-based LEDs performanceis limited by a reduction (droop) of their internal quantum efficiency (IQE) as the driving current density is increased beyond 10 A/cm2, whose physical origin is still under intense debate. In the second part of this thesis, I present a quantum model, based on condensed matter many-body theory, that allowed to obtain the electron capture time and hot-electron intraband relaxation times in a quantum well (QW)-barrier heterostructure, for longitudinal optic (LO) phonon emission, as function of carrier density. The interaction was described in the Single Plasmon Pole of the Random Phase Approximation, retaining the full density-, energy- and wavevector-dependent form of the dielectric function (Chapters 6-7)