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HL: Fachverband Halbleiterphysik

HL 90: Poster Session: Quantum information systems; Optical properties; Ultrafast phenomena

HL 90.4: Poster

Donnerstag, 14. März 2013, 16:00–20:00, Poster A

THz-Transmission Spectroscopy of Charge Carriers in Surface Electric Fields — •Shovon Pal, Nathan Jukam, and Andreas D. Wieck — Applied Solid State Physics, Ruhr University Bochum, Germany

Intersubband transitions take place between quasi-two-dimensional electronic states called subbands, which are formed due to confinement of electrons in the growth direction. Confined electrons in the ground subband absorb incident infrared radiation and are excited to higher subbands, resulting in absorption maxima at intersubband resonance (ISR) frequencies. The absorption wavelength of accumulation and inversion layers lie in the THz domain and hence THz-transmission spectroscopy of these 2D charge carriers serves as an effective tool. A lot of work has been done on intersubband transitions with metallic Schottky gates. But these gates suffer from low breakdown voltages, low transmittance and fails to grow lattice-matched and epitaxially on most compound semiconductors. Epitaxial, complementary doped gates open the possibility to control the charge carrier density to observe the ISR with better optical access. The experimental set-up is being built, which uses a Bruker IFS 113V spectrometer. Semiconductor heterostructures were grown by molecular beam epitaxy (MBE). In the beginning, deposition of a 5 nm semi-transparent gold gate was accomplished by means of UV-photolithography and metallization techniques. The deposition of complementary p-doped gates were performed inside the MBE. The characterization of the heterostructures was done by Hall measurement technique at 300 K and 4.2 K.