Presenter

Sulaiman Rabbaa - ETRO-VUB

Abstract

Nitride-based materials still offer opportunities for the development of new electronic and optoelectronic applications. From the seventies of the 20th century, the GaAs and GaAs/AlGaAs structures were considered as mature family materials for many electronic applications due to their lattice matching and high carrier mobility. In the beginning of the 21th century, these materials are step by step replaced by GaN and GaN/AlGaN structures in many applications due to their high polarization, chemical and physical stability, and wide bandgap.

In this work we study theoretically the electronic and optoelectronic properties of GaN and AlGaN/GaN structures, and we conceive their applications. We test the triangular quantum well model for the high electron mobility transistors (HEMTs). The two dimensional electron gas (2DEG) sheet density and the current-voltage (I-V) characteristics of the AlGaN/GaN HEMT are determined. We discuss in detail the use of GaN-based HEMTs for the design of chemical and biological sensors.

The plasmon frequencies of the 2DEG in the HEMT are calculated. The sensitivity of the tunability of these frequencies is considerable, especially by using a variable applied gate voltage. The interaction between radiation and plasmons has many applications in the terahertz (THz) spectrum. Optoelectronic characterizations of AlGaN/GaN structures with GaAs-Au grating are discussed using full vector diffraction software.

In the context of the optical properties of GaN, we calculate the free-carrier absorption coefficient with strong longitudinal-optical (LO) phonon-plasmon interaction. We take several mechanisms into account, which assist in the photon absorption process. Computations are performed for doped α-GaN and β-GaN at different mid-IR (infrared) wavelengths and doping concentrations.