Regensburg 2019 – wissenschaftliches Programm

Bereiche | Tage | Auswahl | Suche | Aktualisierungen | Downloads | Hilfe

HL: Fachverband Halbleiterphysik

HL 2: Nitrides: Devices

HL 2.2: Vortrag

Montag, 1. April 2019, 09:45–10:00, H31

Metastable Negative Differential Capacitances in GaN-based pn- and tunnel-junctions — •Hartmut Witte, Aqdas Fariza, Silvio Neugebauer, Christoph Berger, Armin Dadgar, and Andre Strittmatter — Institute of Physics, Otto-von-Guericke-University Magdeburg, Universitätsplatz 2, 39106 Magdeburg, Germany

GaN-based tunnel junctions grown by MOVPE are actively investigated to improve current spreading on the p-contact region of pn-junction devices. Low or moderate acceptor doping within the p-doped GaN layer leads to anomalous current-voltage characteristics of pn-junction devices displaying a region of negative differential resistance (NDR). The NDR appears within the low forward voltage region and correlates well with an adequate step in capacitance-voltage characteristics. Both in IV- and in CV-characteristics the NDR effect can be changed by applying voltage pulses. An additional space charge region (SPR) is identified from impedance spectroscopy as origin of the NDR. This SCR acts as a rectifying junction in series with the pn-junction with a capacitance between 10 pF and 50 pF. Capacitance transients show temperature dependent recharging effects of defects with time constants in the range of some ms. On the basis of surface potential measurements by kelvin-probe microscopy GaN:Mg defects are discussed as possible candidates for the NDR effect