Shayne Cairns

Suppression of phonon‐mediated hot carrier relaxation in type‐II InAs/AlAsxSb1 − x quantum wells: a practical route to hot carrier solar cells

InAs/AlAs

Epitaxial growth of elemental Sb quantum wells

_{x}

Observation of surface-state transport in ultrathin Sb

Sb

Remotely-Doped Sb Quantum-Well Structures

_{1-x}

Molecular Beam Epitaxy of Remotely-Doped Sb Quantum-Well Structures

quantum wells are investigated for their potential as hot carrier solar cells. Continuous wave power and temperature dependent photoluminescence indicate a transition in the dominant hot carrier relaxation process from conventional phonon-mediated carrier relaxation below 90 K to a regime where inhibited radiative recombination dominates the hot carrier relaxation at elevated temperatures. At temperatures below 90 K photoluminescence measurements are consistent with type-I quantum wells that exhibit hole localization associated with alloy/interface fluctuations. At elevated temperatures hole delocalization reveals the true type-II band alignment; where it is observed that inhibited radiative recombination due to the spatial separation of the charge carriers dominates hot carrier relaxation. This decoupling of phonon-mediated relaxation results in robust hot carriers at higher temperatures even at lower excitation powers. These results indicate type-II quantum wells offer potential as practical hot carrier systems.

Topological Surface States in Sb Quantum Wells on GaSb(111)A Substrates

An experimental study of growth, structural, and electronic properties of elemental Sb quantum wells with GaSb barriers was performed to explore their potential as topological insulators. A growth procedure on GaAs (111)A substrates was developed to realize ultrathin Sb layers with a thickness of ≤4 nm. Transmission electron microscopy and scanning electron microscopy were used to optimize growth conditions. Resistivity measurements indicated that Sb wells with a thickness above ∼2 nm were metallic (relatively temperature-independent resistivity) whereas thinner wells showed insulating or semiconducting behavior (resistivity increased with decreasing temperature).