Growth and Characterization of AlInSbBi for Wide-Bandgap Barriers on InSb

Abstract

Bi-containing Ill-V alloys have attracted attention over the past few decades due to their suitability for optoelectronic devices operating across a wide spectrum of the infrared region. | Integrating small amounts of Bi into Ill-V materials offers the flexibility to decrease the bandgap energy, which enables infrared emission, and increases spin orbit (SO) split band properties, which can suppress Auger recombination when larger than the bandgap energy. Current approaches for photodetector operation in the mid-wave and long-wave infrared, such as HgCdTe and InSbbased devices, suffer from large dark currents.. While nBn structures can suppress many sources of dark current, the use of AllnSb barriers in InSb-based nBn detectors result in a difficult tradeoff between undesirable valence band offset and high barrier layer strain.4 A flexible method to mitigate these challenges in InSb-based nBn detectors is to introduce small amounts of Bi and Al to InSb to tune the bandgap of InSbBi absorber regions and AllnSbBi barriers, while simultaneously minimizing strain. However, AllnSbBi remains largely underexplored, in part due to the difficulties of growing Bi-containing III-V alloys. Noteworthy are the tradeoffs in temperature and growth rate, which pose *~ In this work, material properties such as bandgap energy, lattice constant, surface morphology, and photoluminescence of AllnSbBi alloys were investigated to optimize material quality for barrier layer applications. AllnSbBi was grown by solid-source molecular beam epitaxy on n-type InSb substrates. To promote Bi incofporation, the substrate temperature was maintained around 300°C and a low VIII flux ratio of 0.975x was employed. The growth rate was chosen to be ~1 um/hr. Atomic force microscopy (AFM) and photoluminescence (PL) measurements were performed on an AllnSbBi thin film targeting ~1% Bi and ~5% Al incorporation. AFM measurements showed droplets on the film surface, however further optimization of the growth parameters may be able to mitigate droplet formation. PL measurements at 83K demonstrated that the AllnSbBi film emitted at roughly 5.1 um, whereas the AllnSb and InSbBi control films emitted at 4.9 and 5.6 um, respectively, suggesting ~0.5% Bi incorporation into AllnSb. To investigate the bandgap change with Bi incorporation, preliminary density functional theory (DFT) simulations with hybrid functionals (HSE) were performed using a 54-atom supercell with 1 Al and 1 Bi atom (corresponding to 3.7% Al and Bi). DFT predicts that the direct bandgap of Alp 037!"9.963°"0 9638/9 037 is reduced by ~20 meV from that of InSb, in qualitative agreement with the observed reduction in PL emission energy. Further growths are underway for additional alloy compositions to fill out the AllnSbBi growth space and optimize the bandgap energy, lattice constant, surface morphology, and photoluminescence to act as a barrier layer. J. J. Lee et. al., Appl. Phys. Lett. 71, (1997). L. Wang et al., Crystals 7, (2017). A. V. Voitsekhovskii and D. I. Gorn, Journ. of Comm. Tech. and Elec. 62, (2017). A. Evirgen et al., Elec. Lett. 50, (2014). M. K. Rajpalke et al., Appl. Phys. Lett. 105, (2014). S. Tixier et al., Appl. Phys. Lett. 82, (2003). R. C. White et al., 21st International Conf. on MBE, (2021).