Ferroelectric gate for control of transport properties of two-dimensional electron gas at AlGaN/GaN heterostructures

The concept of a field-effect transistor with ferroelectric gate has been implemented using the GaN/AlGaN heterostructure combined with Pb(Zr,Ti)O-3 ferroelectric layer. The processing conditions were optimized in a way to obtain textured Pb(Zr,Ti)O-3 films without destroying the two-dimensional electron gas (2D gas) situated at 20 nm below the interface. Poling the ferroelectric layer through the conductive cantilever of the atomic force microscope results in a stable change of resistance of the 2D gas. Concentration and mobility of electrons in the 2D gas were monitored using Hall effect and four-probe conduction measurements in a wide temperature range from 12 to 300 K. The gate polarization oriented in the direction from bottom to top provokes a partial depletion in the channel, resulting in a conductivity decrease by factor of 2.5-3. The depletion effect is found to be reversible so that the initial conductivity in the 2D gas can be restored by depoling the ferroelectric gate. These results indicate that the ferroelectric gate integrated onto the GaN-based system with 2D gas is potentially interesting for nonvolatile memories. Additionally, direct domain writing on a ferroelectric gate represents a flexible and nondestructive way of making rewritable nanopatterns projected onto low-dimensional semiconductor structures. (c) 2006 American Institute of Physics.