Philippe St-Jean

Band gap of sphalerite and chalcopyrite phases of epitaxial ZnSnP2

Using contactless electroreflectance, we determined the band gap of the two known phases of epitaxial ZnSnP2. Induced by small changes in Sn/Zn flux ratio during epitaxy, the order-disordered transition between the chalcopyrite and sphalerite phases reduces the band gap by 300 meV. The chalcopyrite ordered phase, unambiguously identified from x-ray diffraction, exhibits a band gap of 1.683 eV at 293 K. The band gap of the disordered sphalerite phase is 1.383 eV. Using the volume-averaged order parameter measured on the chalcopyrite sample, we find that its morphology is best described by the presence of perfectly ordered domains inside a disordered matrix.

Complete quantum control of exciton qubits bound to isoelectronic centres

In recent years, impressive demonstrations related to quantum information processing have been realized. The scalability of quantum interactions between arbitrary qubits within an array remains however a significant hurdle to the practical realization of a quantum computer. Among the proposed ideas to achieve fully scalable quantum processing, the use of photons is appealing because they can mediate long-range quantum interactions and could serve as buses to build quantum networks. Quantum dots or nitrogen-vacancy centres in diamond can be coupled to light, but the former system lacks optical homogeneity while the latter suffers from a low dipole moment, rendering their large-scale interconnection challenging. Here, through the complete quantum control of exciton qubits, we demonstrate that nitrogen isoelectronic centres in GaAs combine both the uniformity and predictability of atomic defects and the dipole moment of semiconductor quantum dots. This establishes isoelectronic centres as a promising platform for quantum information processing.