Determination of type-I band offsets in GaBi_xAs_1-x quantum wells using polarisation-resolved photovoltage spectroscopy and 12-band k.p calculations

Using photovoltage (PV) spectroscopy we analyse the electronic structure of a series of GaBi_xAs/(Al)GaAs dilute bismide quantum well (QW) laser structures. The use of polarisation-resolved PV measurements allows us to separately identify transitions involving bound light- and heavy-hole States in the QWs, as well as bound-to-continuum transitions from the QWs to the barriers. Analysis of these transitions enables us to probe the GaBi_xAs/(Al)GaAs conduction and valence band offsets, thereby quantifying the band offsets. Using a 12-band Hamiltonian, we extract the band offsets in the QWs explicitly by constraining the Bi-related parameters of the model against the experimentally measured transition energies. The PV measurements and calculations we present provide the first explicit confirmation of a type-I band offset at the GaBi_xAs/GaAs heterointerface near x = 2%. This result, combined with the theory we present for calculating the band offsets at GaBi_xAs/(Al)GaAs heterointerfaces, can be used to determine the band offsets at arbitrary Bi composition x.