The electronic quasi-bound state in the continuum concept is explored in an InGaAs/InAlAs heterostructure to create a voltage-tunable dual-colour quantum Bragg mirror detector. This heterostructure is based on one main quantum well embedded between two different superlattices. By bandgap engineering, each superlattice gives rise to quasi-bound states in the continuum with a preferential direction for electron extraction. Due to these states, the photovoltaic photocurrent presents a dual-colour response, one in a positive direction at 340 meV (3.6 µm), and one in a negative direction at 430 meV (2.9 µm). The simultaneous dual-colour detection can be switched to a single-colour detection (340 meV or 430 meV) by applying a bias voltage. At 77 K, the specific detectivity for simultaneous dual-colour is 2.5·108 Jones, while the single-colour detectivities are 2.6·109 Jones at +2.0 V and 7.7·108 Jones at −1.6 V for 340 meV and 430 meV, respectively.

The viability of epitaxial regrowth of non-intentionally doped InP to passivate lateral mesa surfaces of InGaAs photodiodes lattice-matched to InP is investigated, evaluating whether the residual doping of the regrown layer can be responsible for an unexpected increase of the surface current. The effect of residual doping is evaluated via numerical calculations of dark current, considering the range of doping concentrations expected for non-intentionally doped InP. The calculations show that the increase in dark current due to the residual doping of the regrown InP layer is not enough to justify the observed increase in surface current. On the other hand, the technique is still valid as a passivation method if the photodetector pixel is isolated by etching only the top contact layer.