Materials study of the competing group-V element incorporation process in dilute-nitride films
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1202-I05-24
Materials study of the competing group-V element incorporation process in dilute-nitride films Wendy L. Sarney and Stefan P. Svensson U.S. Army Research Laboratory, Sensors & Electron Devices Directorate, Adelphi, MD 20783, U.S.A. ABSTRACT The incorporation of small amounts of N into III-V antimonide-containing semiconductor alloys allows a drastic expansion of available wavelengths for infrared (IR) detector applications. Quaternary films containing three group-V elements can be lattice matched to the most prevalent substrates for IR applications, such as InAs, GaAs, and GaSb. It is not trivial to incorporate N while maintaining the high crystalline quality required for IR devices. Current materials characterization studies of dilute-nitride films consisting of more than two group-V elements has yielded conflicting information related to their competing behavior and the extent of N incorporation. Due to challenges related to light-element microanalysis for many characterization techniques, and the small concentrations of N involved, it is difficult to quantify the amount of N incorporated into dilute-nitride films. In this study, we use transmission electron microscopy (TEM), energy-dispersive spectroscopy (EDS), and x-ray diffraction (XRD) to study the incorporation behaviors of the competing group-V elements in InAsSbN films. INTRODUCTION Dilute nitride semiconductors contain a small amount of N (typically less than 5%) incorporated into a III-V compound. Adding small concentrations of N dramatically expands the range of accessible wavelengths, as shown in Fig. 1. The green region shows the range of wavelengths available with the common III-V semiconductors, and the blue region shows the additional wavelengths that can be obtained by incorporating N. Early work in the dilute-nitrides was related to alloys that were lattice matched to GaAs for the purpose of reaching the 1.3-1.6 µm wavelength, which is suitable for optoelectronic 2.5 AlP AlAs
1.5
0.62
AlSb GaAs
0.83 InP
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1.24 GaSb
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InSb
InAs 0.0 5.4
5.6
5.8 6.0 6.2 Lattice Constant (Å)
6.4
Wavelength (µm)
Bandgap (eV)
2.0 GaP
3.10 6.20 12.40
6.6
Figure 1: Bandgaps and corresponding wavelengths for III-V semiconductors
telecommunication applications [1]. There is recent interest in materials that are lattice matched to GaSb or InSb for IR detector applications [2-3]. Alloys based on GaAs, GaSb, or InAs do not naturally have the bandgaps needed for long-wave IR (LWIR) detector applications requiring operating wavelengths greater than 5 µm. The bandgap for GaAs, for instance, is 1.42 eV, which is in the near-infrared (NIR) range. For this reason, quantum structures such as quantum well IR photodetectors (QWIPs) and type-II strained-layer superlattices are grown to take advantage of confinement effects and to induce an effective bandgap in the desired range. The disadvantage of such structures is that they require many interfaces which must be atomically precise, and the quality of such films may be fundamentally limited. The dil
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