We report the observation of two negative conductance regions in the low-temperature photocurrent-voltage characteristic of tight-binding multiquantum well (35 periods) 1-μm-thick Al0.48 In0.52As/ Ga0.47 In0.53As superlattices grown by molecular beam epitaxy. The two peaks occur at voltages corresponding to a potential energy drop across the superlattice period equal to the energy differences between the first two excited states and the ground state of the quantum wells. This provides direct evidence of sequential resonant tunneling between the ground and excited states of adjacent wells alternated with intrawell energy relaxation.
We have succeeded for the first time in artificially tuning the conduction and valence-band barrier heights at an abrupt intrinsic semiconductor-semiconductor heterojunction via a doping interface dipole (DID). This is achieved by means of ultrathin ionized donor and acceptor sheets in situ grown within ≲100 Å from the heterointerface by molecular beam epitaxy. In the limit of a few atomic layers separation between the charge sheets this amounts to modify the effective band-edge discontinuities. A near one order of magnitude enhancement in the photocollection efficiency of an abrupt AlGaAs/GaAs heterojunction has been observed as result of the conduction-band barrier lowering induced by the DID.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.