Figure 1.
1a, A schematic showing Bi (purple) replacing As (red) in GaAs.
1b, A simplified diagram of the effect of 4 % Bi on the energy bands of GaAs.
1c, The bandgap energy and spin-orbit splitting energy of free-standing and strained GaAsBi, the coloured dots represent the different Bi content samples characterised in this paper.
1d, Schematic cross-section of the p‑i‑n (n‑i‑p) device structures used in this investigation.
1e, Absorption coefficient vs wavelength for a range of Bi contents compared to silicon and GaAs.

Figure 2.
2a (b), The symbols show Me (Mh) versus applied reverse bias for p-i-n (n-i-p) structures of varying i-region thickness while the solid lines show the dark currents for 50–100 µm diameter devices.
2c (d), Me-1 (Mh-1) vs electric field for the 400 nm thick p-i-n (n-i-p) diodes of different Bi contents. The solid lines show the simulated results.
2e, a vs inverse electric field at a range of Bi contents; inset shows a versus Bi content at an inverse electric field of 3 × 10-6 cm/V.
2f, b of GaAsBi vs inverse electric field for a range of Bi contents.

Figure 3.
3a, The minimum electric field required to cause electrons and holes to ionize (defined as when Me,h = 1.01) in nominally 400 nm GaAsBi p-i-ns and n-i-ps.
3b, The a/b ratio (at Me = 1.1) in GaAsBi as a function of the ∆so energy.
3c, The calculated electric-field dependence of the a/b ratio for different Bi contents.
3d, The measured excess noise.
3e, The simulated excess noise (Fe) at M = 10 for 1500 nm thick avalanching structures with increasing Bi content.