Probing N- and Bi-related states in GaAsNBi/GaAs heterostructures

Due to the complementary impacts of N and Bi on the GaAs band structure, N-Bi co-alloying to form GaAsNBi provides significant opportunities for band structure engineering. It has been predicted that N (Bi) incorporation primarily impacts the conduction (valence) band of GaAs, while introducing tensile (compressive) in-plane lattice strain with respect to a GaAs substrate. To explore the N- and Bi-related states near the conduction and valence band edges, we are examining the electronic properties of diodes containing n-GaAs/GaAs(N)(Bi)/n-GaAs quantum wells (QWs) with various N and Bi fractions. Using capacitance-voltage (C-V) measurements interpreted within the depletion approximation, we profile the free carrier concentrations across the QWs. To quantify the conduction band offsets (CBO), we compare the C-V-determined carrier concentration profiles with those computed using 1D Schrödinger-Poisson simulations in the effective mass approximation. Given the mole fractions of N and Bi from x-ray rocking curves and Rutherford backscattering spectrometry, we then associate CBO values with specific alloy compositions. In addition to discussing the composition dependence of the band offsets, we will discuss our progress towards probing Bi-related states.