| AVS 62nd International Symposium & Exhibition | |
| Spectroscopic Ellipsometry Focus Topic | Thursday Sessions |
| Session EL+EM+EN-ThM |
| Session: | Spectroscopic Ellipsometry: Novel Applications and Theoretical Approaches |
| Presenter: | Sean Knight, University of Nebraska-Lincoln |
| Authors: | S. Knight, University of Nebraska-Lincoln S. Schöche, J.A. Woollam Co. Inc. V. Darakchieva, Linköping University, Sweden P. Kühne, Linköping University, Sweden J.-F. Carlin, Ecole Polytechnique Fédérale de Lausanne (EPFL), Switzerland N. Grandjean, Ecole Polytechnique Fédérale de Lausanne (EPFL), Switzerland C.M. Herzinger, J.A. Woollam Co. Inc. M. Schubert, University of Nebraska-Lincoln T. Hofmann, University of Nebraska-Lincoln |
| Correspondent: | Click to Email |
The terahertz optical Hall effect (THz-OHE) has been established as a non-contact and therefore valuable tool for the investigation of free charge carrier properties in semiconductor heterostructures [1-4]. In this work, we demonstrate that the THz-OHE signal for samples grown on THz transparent substrates can be controlled and enhanced by a tunable, externally coupled Fabry-Pérot cavity mode [5]. An AlInN/GaN-based high electron mobility transistor structure (HEMT) grown on a sapphire substrate is investigated as an example, while the cavity enhancement phenomenon discussed here is generally applicable to situations when a layered sample is deposited onto a THz transparent substrate. We show that in the vicinity of an externally coupled-cavity mode, a strong enhancement of the OHE signatures of up to one order of magnitude can be achieved by optimizing the cavity geometry, which is very useful for small magnetic field strengths. This signal enhancement allows the determination of free charge carrier effective mass, mobility, and density parameters using OHE measurements in low magnetic fields. Previously, high-field electromagnets needed to be employed for THz-OHE measurement for the determination of free charge carrier parameters in semiconductor heterostructures. Tuning the external cavity allows an enhancement of the THz-OHE signatures by as much as one order of magnitude. We propose to employ this enhancement effect to reliably and accurately determine free charge carrier properties in semiconductor structures at small magnetic fields dispensing with the need for expensive high magnetic fields. Cavity-enhanced THz-OHE may therefore enable the wide spread contactless measurement of free charge carrier properties at THz frequencies and which is indispensable for the development of the next generation of group-III nitride-based high frequency devices.