Investigation of Electrical Transport in Semiconductor Heterostructure Devices Coupled Strongly to the Light Field

Intersubband Polaritons [1] are quasi-particles that form under strong light-matter coupling conditions in semiconductor heterostructures. The two main requirements are a high-Q tunable cavity and a suitable intersubband transition. Intersubband polaritons are predicted to enable novel applications such as the intersubband polariton laser [2]. The most characteristic feature of intersubband polaritons is their avoided-crossing property. When the detuning between the cavity resonance and the intersubband transition is very small (i.e. the cavity resonance frequency equals the intersubband transition energy) the two absorptions caused by the cavity and the intersubband transitions become indistinguishable. For the matter part we used triple-barrier resonant tunneling diodes (TBRTDs) [3]. TBRTDs are semiconductor heterostructures that consist of two quantum wells. When applying an electric field, the eigen-energies of the quantum wells can align, which leads to a resonant tunneling current. This causes sharp peaks in the I-V-characteristic of the devices. TBRTDs also feature intersubband transitions, which are crucial for the formation of intersubband polaritons. The intersubband transition of interest is located at 100 meV.