Dresden 2014 – scientific programme

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HL: Fachverband Halbleiterphysik

HL 68: Heterostructures and interfaces

HL 68.7: Talk

Wednesday, April 2, 2014, 16:30–16:45, POT 051

THz Transmission Spectroscopy of Charge Carriers in Semiconductor Heterostructures with epitaxial, complementary doped gate — •Shovon Pal^1,2, Hanond Nong², Sascha Valentin¹, Arne Ludwig¹, Nathan Jukam², and Andreas D. Wieck¹ — ¹Lehrstuhl für Angewandte Festkörperphysik, Ruhr-Universität Bochum — ²Arbeitsgruppe Terahertz-Spektroskopie und Technologie, Ruhr-Universität Bochum

Intersubband transitions take place between quasi-two-dimensional (2D) 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 transmission minima at intersubband resonance (ISR) frequencies. These frequencies lie in the THz domain and hence THz-transmission spectroscopy of these 2D charge carriers serves as an effective tool to investigate ISR. In the present work, an epitaxial, complementarly doped gate is used to control the 2D electron density in a modulation doped GaAs-AlxGa(1-x)As heterojunction to observe the ISR. Hall measurements of the sample show that the 2D electron density is n=1.76e11 cm-2. Density chopping measurements between the threshold voltage (n=0) and a certain gate voltage (n) were performed with the sample tilted at 30°, normalizing the transmission spectra T(n) via division by T(0). With a magnetic field in beam direction and the sample tilted at the same angle as before, half-field coupling of the cyclotron resonance with the ISR was observed. All measurements were performed at 4.2 K.