Nakayama, M.M.NakayamaAndo, M.M.AndoTanaka, I.I.TanakaNishimura, H.H.NishimuraSchneider, H.H.SchneiderFujiwara, K.K.Fujiwara2022-03-032022-03-031995https://publica.fraunhofer.de/handle/publica/18610110.1103/PhysRevB.51.4236We have investigated electric-field effects on the above-barrier states in a GaAs (7.0 nm)/Al sub0.1 Ga sub0.9 As (3.5 nm) superlattice clad by p-type and n-type Al sub0.3 Ga sub0.7 As layers using electroreflectance spectroscopy for detecting the interband optical transitions and using a transfer-matrix method for calculating the eigenenergies. It is demonstrated that the electric-field dependence of the energies of the optical transitions associated with the above-barrier states exhibits a similar feature of the Stark-ladder states below the barrier potential. In addition, it is found from the line-shape change of the electroreflectance signals that the above-barrier state resonantly couples with the spatially separated below-barrier state. The lineshape change results from the formation of bonding and antibonding states and wave-function delocalization over the coupling space. The transfer-matrix analysis explains the above experimental results reasonably well.enHalbleitersemiconductorsuperlatticeÜbergitterWannier-Stark localizationWannier-Stark-Lokalisierung621667530journal article