InPBi Single Crystals Grown by Molecular Beam Epitaxy

Abstract

InPBi was predicted to be the most robust infrared optoelectronic material but also the most difficult to synthesize within In-VBi (V = P, As and Sb) 25 years ago. We report the first successful growth of InPBi single crystals with Bi concentration far beyond the doping level by gas source molecular beam epitaxy. The InPBi thin films reveal excellent surface, structural and optical qualities making it a promising new III–V compound family member for heterostructures. The Bi concentration is found to be 2.4 ± 0.4% with 94 ± 5% Bi atoms at substitutional sites. Optical absorption indicates a band gap of 1.23 eV at room temperature while photoluminescence shows unexpectedly strong and broad light emission at 1.4–2.7 μm which can't be explained by the existing theory.

Novel Dilute Bismide, Epitaxy, Physical Properties and Device Application

“…Hosea et al quantified this value of about 0.33 ± 0.07 meV/K by PL and PR measurements which is independent upon Bi concentration [178]. Contrary to these results, Yi et al [116] discovered that incorporating Bi into InGaAsBi/GaAs QW could extensively improve PL intensity and emission wavelength, but not the temperature sensitivity of bandgap. This unexpected behavior from the Bi-containing QW is attributed to a small Bi content of only 0.6%.…”

“…However, incorporation of Bi is usually non-uniform in the matrix, which makes PL quite broad. Enhancement of PL intensity accompanied by a broadening effect of full-width at half-maximum (FWHM) has been observed in InGaAsBi/GaAs QWs [115], InPBi [116], InGaPBi [117] and InAlPBi [118].…”

“…The lattice constant for ZB InBi is around 6.5 Å [116,158], which is quite large comparing to 5.858 Å of InP. So the lattice constant of InPBi should be between that of InP and InBi.…”

“…Due to synthesis challenges, InPBi crystals were first realized by Wang et al using gas source MBE in 2013 [116] which is 25 years after the theoretical prediction. It showes several abnormal properties comparing with other dilute bismides, especially for its optical property.…”

Incorporation of Bi atoms in InP studied at the atomic scale by cross-sectional scanning tunneling microscopy

“…Until now, most experimental studies of the MBE growth of highly mismatched III-V bismides, such as GaAs 1-x Bi x [5,6], InAs 1-x Bi x [7,8], and InP 1-x Bi x [4,9,10], are limited to the improvement of the growth conditions and the optical characterization of their material properties. In contrast to other highly mismatched III-V bismides, which are grown at low temperatures by MBE, Bi:InP shows additional strong optical transitions at lower energies than the commonly observed band-to-band transitions [4,9,11].…”