InAsNSb Dilute Nitride Materials for Mid-infrared Devices & Applications

Lead Research Organisation: University of Nottingham
Department Name: Sch of Physics & Astronomy

Abstract

We aim to achieve a breakthrough in the performance of "dilute nitride" semiconductor materials to enable the development of novel light sources and photodetectors which can operate in the mid-infrared spectral range. The 3-5 um wavelength range is technologically important because it is used for applications including; remote gas sensing, range-finding and night vision, bio-medical imaging for diagnosis in healthcare and sensitive detection in optical spectroscopy.
However, the development of instrumentation is limited by the availability of efficient, affordable light sources and photodetectors, which is directly determined by the semiconductor materials which are currently available. By introducing small amounts (~ 1%) of N into InAs(Sb) we have shown that it is possible to access the mid-infrared using a new (dilute nitride) semiconductor and we are now seeking to engineer its band structure in order to significantly enhance the material's optical properties and increase quantum efficiency for light detection and emission.

To enable the development of new photodetectors we will exploit the sensitivity of the conduction band to the resonant interaction of the N-level with the extended states of the host InAsSb crystal lattice to tailor the photoresponse and create a near ideal situation for electron acceleration and avalanche multiplication, resulting in a much larger detectable signal. To minimise the unwanted processes causing excessive noise and dark current, which compete with the avalanche multiplication and light detection in the detector, we shall arrange for the avalanche multiplication to be initiated by only one carrier type (electrons in our case). Many applications rely on the detection of very weak signals consisting of only a few photons. Conventional photodiodes have a limited sensitivity, especially if high speed detection is needed. In applications which are "photon starved", avalanche photodiodes (APDs) can provide an effective solution. However, at present effective avalanche multiplication in the mid-infrared spectral range can only be obtained by using exotic CdHgTe (CMT) semiconductor alloys. The resulting detectors require cooling, thus making CMT-based APDs prohibitively expensive for all except military applications. Simpler fabrication, low noise, low operating voltage, inexpensive manufacturing and room temperature operation, together with monopolar electron ionisation are all significant advantages of APDs based on the dilute nitride materials compared to existing technologies. Similarly, we shall enable the development of more efficient mid-infrared light sources. By adjusting the N content within InAsN(Sb) quantum wells and carefully tailoring the residual strain and carrier confinement, we shall be able to defeat competing non-radiative recombination processes whilst simultaneously enhancing the light generation efficiency. These novel quantum wells would then form the basis of the active region from where the light is generated, either within an LED or a diode laser. Currently mid-infrared LED efficiency is low at room temperature, and with the improvements which we shall deliver; we envisage that devices with significantly higher dc output power will be developed following our lead. Mid-infrared diode lasers incorporating our strained dilute nitride quantum wells are also expected to exhibit a reduced threshold current and could offer an affordable alternative to existing technology, especially in the 3-4 um spectral range. We will produce prototype photodetectors and LEDs and use these to demonstrate the above-mentioned avalanche behaviour and quantum efficiency improvements respectively. We shall validate our dilute nitride materials and structures in close collaboration with our collaborators at NPL, SELEX, CST and INSTRO to evaluate performance for use in practical applications and help ensure uptake of our technology.

Publications

10 25 50
 
Description We have obtained fundamental information concerning the incorporation, properties and behaviour of N in InAs based semiconductors for levels of N~1%. In addition to the reduction of the energy gap, we observed that addition of N causes a reduction in the radiative efficiency for light generation and produces a corresponding increase in the residual electron concentration.

We have reported a novel linear magnetoresistance phenomenon that arises from multiple scattering of the current-carrying electrons by macroscopic disordered regions of the InAsN alloy. Monte Carlo computer simulations of the electron motion confirmed the experimental observations at magnetic fields up to 50T, thus unravelling the origin of the linear magnetoresistance and opening new ways of controlling it.

Together with University of Rome we obtained new information on the effects of hydrogen in InAs(Sb)N dilute nitrides: we observed a substantial increase in the electron concentration due to H and recovery of the radiative efficiency, which was also obtained using rapid thermal annealing. In particular, we have demonstrated that the surface conductivity of InAsN can be significantly increased by the incorporation of hydrogen. For a fixed dose of impinging H-atoms on the surface, the width of the surface conducting channel decreases with increasing concentration of N-atoms, which act as H-traps thus forming N-H donor complexes near the surface. The hydrogen incorporation also induces plasmonic effects that can be controlled/reversed by laser annealing.

We have demonstrated prototype mid-infrared devices including InAsN p-i-n diode photodetectors produced by ion implantation and obtained evidence of multiplication in APDs. We also produced InAsN quantum well LEDs and photodetectors, and recently demonstrated the first InAsN resonant tunnelling diodes.
Exploitation Route Our observations and modelling of the linear magnetoresistance are applicable to other disordered systems. Our prototype LEDs and detectors represent the first step towards enabling new capabilities in mid-infrared sensing and imaging following further improvements in quantum efficiency. The fundamental information produced will be useful to device designers and engineers developing photonic components and systems. The resonant tunnelling diodes will be of interest to electronic engineers: they demonstrate a novel mechanism for negative differential resistance due to N-induced localized states in the energy gap of InAsN and weakly affected by temperature. The functionalization of the surface by hydrogen and the corresponding modulation of the surface conductivity can provide a platform for several important applications, including gas sensing, "all semiconductors" plasmonic waveguides, and printed circuits.
Sectors Education,Electronics

 
Description The investigation of the novel semiconductor alloy InAsN and of the effects of hydrogen has stimulated interdisciplinary international collaborations within the Initial Training Network PROMIS (http://www.physics.lancs.ac.uk/promis/). Our work explores plasmonic applications of (InAsN) in the mid-infrared (MIR) spectral range, which is relevant for detection of selected gas and molecular fingerprints at target wavelengths. This work has led to additional publications associated to both the ITN and this EPSRC project.
First Year Of Impact 2016
Sector Education,Electronics,Environment
Impact Types Cultural

 
Description EU-ITN, Postgraduate Research on Dilute Metamorphic Nanostructures and Metamaterials in Semiconductor Photonics "PROMIS"
Amount € 262,000 (EUR)
Funding ID 641899 
Organisation European Commission 
Sector Public
Country European Union (EU)
Start 01/2015 
End 12/2019
 
Description Nottingham/Osaka partnership on the modelling of mobility and magnetoresistance in non-homogeneous high-mobility semiconductors and hybrid systems 
Organisation Osaka University
Country Japan 
Sector Academic/University 
PI Contribution Experiments were performed in Nottingham/Dresden and modelled in collaboration with our partner in Japan.
Collaborator Contribution Experimental data were modelled by our partner in Japan.
Impact This partnership led to research articles, as listed in the separate list of publications.
Start Year 2012
 
Description Nottingham/Rome partnership to study the effects of hydrogen dopants in In(AsN) 
Organisation Sapienza University of Rome
Country Italy 
Sector Academic/University 
PI Contribution We provided evidence for the unique effect of hydrogen on the transport properties of the mid-infrared alloy In(AsN). High electron concentrations and mobilities are simultaneously achieved in hydrogenated In(AsN), and Shubnikov-de Haas oscillations are observed up to near room temperature. These results can be accounted for by the formation of N-H donor complexes with energy levels well above the Fermi energy, far from resonance with the conduction electrons, thus resulting in weak electron scattering even at high donor concentrations. Similar effects should be found in other narrow band gap dilute nitride alloys
Collaborator Contribution Our partner contributed to this research by performing the hydrogenation of our samples using their facilities in Rome.
Impact Several research articles, as indicated in the separate list of publications.
Start Year 2012
 
Description Contributed talk at "EDISON 2013", Matsue, Japan 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Postgraduate students
Results and Impact Report on linear magnetoresistance due to multiple-electron scattering by low-mobility islands in an inhomogeneous conductor.
Year(s) Of Engagement Activity 2013
 
Description Invited talk at "UK Semiconductors", Sheffield UK 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Postgraduate students
Results and Impact Linear magnetoresistance due to multiple-electron scattering by low-mobility islands in an inhomogeneous conductor

Linear transverse magnetoresistance is commonly observed in many material systems including semimetals, narrow band-gap semiconductors, multi-layer graphene and topological insulators. It can originate in an inhomogeneous conductor from distortions in the current paths induced by macroscopic spatial fluctuations in the carrier mobility and it has been explained using a phenomenological semiclassical random resistor network model. However, the link between the linear magnetoresistance and the microscopic nature of the electron dynamics remains unknown. Here we demonstrate how the linear magnetoresistance arises from the stochastic behaviour of the electronic cycloidal trajectories around low-mobility islands in high-mobility inhomogeneous conductors and that this process is only weakly affected by the applied electric field strength. Also, we establish a quantitative link between the island morphology and the strength of linear magnetoresistance of relevance for future applications.
Year(s) Of Engagement Activity 2013