May 25, 2010
Polarization enables dopant-free nanowire devices
Control of the polarization fields is the most important parameter in designing III-nitride thin-film high-electron-mobility transistors (HEMTs) and light-emitting diodes (LEDs). Now, scientists at NRL have demonstrated that the polarization fields are equally if not more important in devising III-nitride nanowire devices. Control of these polarization fields has enabled the fabrication of an undoped AlGaN shell/GaN core nanowire transistor with p-type conductivity based solely on polarization-induced hole carriers at the (000-1) interface.
Charge control in the vast majority of semiconductor devices is based on electron or hole carriers ionized from dopant atoms intentionally introduced into the semiconductor crystal. In contrast, polarization-induced carriers do not originate from dopant atoms and thus avoid deleterious ionized impurity scattering. Furthermore, it is possible to design a nanowire with a large accumulation of polarization-induced holes and electrons at opposing facets. The close proximity of the two polarization-induced charges could lead to nanowire light emitters or photovoltaics with enhanced efficiency.
The researchers presented their work in the journal Nanotechnology.
About the author
Michael Mastro is currently a civilian staff scientist at the US Naval Research Lab. His research interest is the growth and design of thin-film and nanowire semiconductor devices.