Berlin 2015 – wissenschaftliches Programm
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HL: Fachverband Halbleiterphysik
HL 40: Focus Session: Role of polarization fields in nitride devices I
HL 40.1: Hauptvortrag
Mittwoch, 18. März 2015, 09:30–10:00, ER 164
Boon and bane of polarization induced effects in group III-nitride based heterostructures — •Oliver Ambacher — Fraunhofer Institute for Applied Solid State Physics, Freiburg, Germany
Gradients of spontaneous and piezoelectric polarization at surfaces and interfaces of group III-nitride based heterostructures having hexagonal crystal structure can cause huge sheet charges. These fixed sheet charges dominate the band edge as well as the concentration profiles of free carriers. Boon of polarization induced effects are high mobility two dimensional carrier gases with large sheet concentration appearing without intentional doping and opening up new concepts for high power as well as for high frequency transistors. Boon and bane is the sensitivity of polarization induced carrier profiles towards any change of surface potential which might be caused by charged defects, ions or polar molecules. This effect makes it very difficult to achieve suitable surface passivation and long term stable group III-nitride based electronics but opens up an interesting field of very charge sensitive devices suitable for pH-sensors or the detection dangerous polar molecules in gases and liquids. Based on an explanation of non-linear spontaneous and piezoelectric polarization in ternary group III-nitride hexagonal crystals (c−AlxM1−xN, M:= Ga, In, Sc) the state of the art as well as novel electronic and sensor devices will be presented