High magnetic field far-infrared spectroscopy of spatially separated electron-hole layers

Cyclotron resonance (CR) experiments have been performed on InAs/GaSb structures, in which InAs (electron) and GaSb (hole) layers are separated by AlSb barriers. Our data reveal that properties of InAs/GaSb systems with AlSb barriers thinner than 1.5 nm are entirely determined by interlayer tunneling and the CR features in such samples can be explained by hybridization between states in the InAs conduction band and in the GaSb valence band. The hybridization gap has been estimated from CR spectra for two samples with different degrees of electron-hole coupling. The CR spectra of widely separated electron-hole layers (with barriers thicker than 2 nm) are characterized by pronounced spin splitting. In addition to multiple spin-split CR lines new lines have been observed at high magnetic fields (11-13 T).