Conference Agenda

The spontaneous polarization Pspont is a key property of the wurtzite III-N

semiconductors AlN, GaN and InN and a unique feature compared to

alternative semiconductor classes like Si, SiC or GaAs. While previously, the

direction and magnitude of Pspont in III-Ns was exclusively determined

during film growth, ferroelectricity now allows to select and measure

direction and net-magnitude of Pspont through the application of external

bias. Intense research on adding non-volatile memory functionality,

tailored excitation of higher acoustic modes and functional domain walls to

III-N technology has therefore commenced and is in the process of

extending to optoelectronics. At the same time, chances are that the ability

to measure Pspont will reverberate strongly to established III-N technology,

as it provided experimental evidence that Pspont of GaN, AlN and InN

surpasses conventional wisdom by more than one order of magnitude. This

development should lead to new design paradigm for e.g. the polarization

based GaN high electron mobility transistor (HEMT).

In addition to highlighting how ferroelectricity can thus shape a new

perspective on III-N semiconductors, this contribution will discuss recent

progress towards understanding and harnessing the implications of

ferroelectric domains in III-Ns: electric field induced polarization

discontinuities are apparently able to concentrate massive bound charge

(~ 200 µC/cm²) in atomically sharp interfaces. This bound charge in turn

induces conductive sheets that can e.g. directly serve for the purpose of

resistive memories. On/off ratios and operating voltages attractive for inmemory computing are demonstrated.

Vertical GaN devices typically suffer from high reverse leakage currents and premature breakdown due to the etch damage caused by chlorine-based reactive ion etching (RIE) during fabrication. This study examines the impact of such etch damage and evaluates the effectiveness of various post-etch treatments on regrown GaN pn diodes. A single low-power CF₄ plasma treatment proves highly effective in reducing etch damage and removing contaminations from the surface before regrowth, significantly lowering reverse leakage currents. However, it also increases the diode on-resistance, likely due to fluorine passivation. To address this, an in-situ trimethylgallium (TMGa) flushing step at 400 °C following the ex-situ CF₄ plasma treatment successfully removes such fluorine species, reducing on-resistance and further enhancing electrical performance to a level comparable to that of continuously grown pn diodes.

The thermal enhancement and the behavior of GaN Schottky diodes grown by metal organic chemical vapor deposition (MOCVD) on sapphire substrates has been investigated. Pt/Au anodes annealed at 500 °C and 600 °C show an improvement of the electrical characteristics and a breakdown voltage as high as 130 V for a drift layer thickness of 1 μm and a doping of 1016 cm-3.

The performance of GaN Schottky barrier diodes and high electron mobility transistors as mm-wave power detectors is measured and interpreted in terms of analytical and equivalent circuit models. The dependence of the results on the device geometry, bias, frequency and temperature is analyzed.

In this work, we propose a model to discern between the perimeter and area contributes of the p-GaN HEMTs gate current density. The perimeter and area contributes of the gate current density were evaluated on HEMTs of different geometry. Then, temperature dependent electrical measurements allowed to extrapolate the Schottky barrier height (1.18 eV) and the p-GaN doping level (4.1×1018 cm-3) of the p-GaN layer.