Study Of Inas/Ga(In)Sb And Inasn/Ga(In)Sb Superlattices By Mbe For Very Long Wavelength Infrared Photodetectors

Infrared (IR) sensors are extremely important in missile defense as well as in satellite-based infrared detection systems. Long-range ballistic missile defense for incoming missile acquisition, tracking, and discrimination requires space-based infrared technology. Hence long wavelength and very long wavelength infrared regimes are extremely important for such applications. The focus of this work is on the investigation of superlattices (SLs) and in particular dilute nitride based SLs for such applications in this infrared region. A comprehensive study of InAs/GaSb, InAs/GaInSb, InAsN/GaSb and InAsN/GaInSb SLs grown by molecular beam epitaxy (MBE) has been carried out using different characterization techniques. Optimization of the structures with growth parameters such as interfacial layers, layer thickness, and material composition will also be discussed. The judicious selection of the above combination of parameters was abetted by theoretical simulation using OPTEL_ZB software. A systematic and detailed study has been made correlating the structural quality, vibrational modes, scanning transmission electron microscope (STEM) micrographs and optical properties of each of the optimized structure of the SL. All the SLs were defect free with sharp interfaces and well defined sublayers as attested by high resolution x-ray diffraction (HRXRD) and asymmetric reciprocal space mapping (RSM) spectra as well as STEM images. The unique feature of this work is the growth of InAsN/GaSb SL which has not been reported elsewhere to the best of our knowledge. This SL shows promise in that thinner layers of InAsN were used for the same strain balancing effect as thicker InAs. Hence the former would improve optical absorption. Since the N in InAsN reduces the overall lattice constant of the material system it added another degree of freedom in strain balancing the structure to the GaSb substrate. A cut off wavelength of ~20 μm was achieved with the InAsN/GaSb SL

Growth and characterisation of dilute antimonide nitride materials for long-wavelength applications

The addition of small amounts of nitrogen to III-V semiconductors leads to a large degree of band gap bowing, giving rise to band-gaps smaller than in the associated binary materials. The incorporation of active nitrogen has been previously demonstrated for InNxSb1-x (x <= 0.7%) and GaNxSb1-x (x <= 1.75%) material; however, the as-grown carrier concentrations precluded incorporation into a device structure. Here we report the reduction in the as-grown carrier concentration in InNSb by annealing, whilst retaining the active nitrogen content. FTIR absorption measurements show the first direct experimental evidence of narrowing of the InSb bandgap due to nitrogen incorporation. As an alternative route to defect reduction and device compatible material we report on the growth of Ga1-yInyNxSb1-x, with 0 <= y <= 30% and x = 1.6 +/- 0.2% and demonstrate near lattice matching of the material to GaSb. (C) 2008 Elsevier Ltd. All rights reserved

Study Of N Incorporation In Insb On Gaas By Molecular Beam Epitaxy For Long Wavelength Infrared Devices

The distinguishing features of dilute nitride III-V semiconductors lie in the large simultaneous reduction in the band gap and lattice parameter when N is incorporated in small amounts in an otherwise wide band gap III-V material. In particular, N incorporation in InSb is attracting great attention due to its potential applications in the long wavelength infrared (LWIR) applications. However, the relatively small atomic size of N with respect to Sb makes the growth of good quality InSbN layers challenging with effective N incorporation. In this dissertation we present a correlation of the molecular beam epitaxial growth parameters on the type of N-bonding in the InSbN epilayers. Lower growth temperatures of ~290 °C were observed to favor formation of more substitutional N (In−N) and less interstitial N (Sb−N, N−N and In−N−Sb) in the InSbN epilayers. The types of N-bonding were observed to have dominant effect on the structural, vibrational, electrical and optical properties of these dilute nitride epilayers grown on GaAs substrates. As-grown epilayers with high N incorporation of 2.6 % were observed to exhibit a blue shift in the absorption edge to 0.132 eV due to Moss-Burstein effect. Both ex-situ and in-situ annealing at 430 °C improved the quality of the layers as attested to by the micro-Raman spectra, reduced the carrier concentration to ~1016 cm-3 , increased the mobility (µ) to ~13,000 cm2 /V-s and red shift the absorption edge to ~10 µm at room temperature (RT). Amongst the heterostructures examined, consisting of different combination of thickness of InSb and InSbN layers, the growth of a relatively thick (~1.4 µm) InSb buffer layer was found to prevent the propagation of rotational and threading dislocations into the subsequent InSbN epilayers. Thus, high RT µ exceeding 40,000 cm2 /Vs and an optical absorption edge at ~12 µm in the LWIR range have been achieved for 450 °C ex-situ annealed 0.4 µm InSbN/ 1.4 µm InSb/ GaAs heterostructure