Studies of metal–ferroelectric–GaN structures

A GaN-based metal–insulator–semiconductor (MIS) structure has been fabricated by using ferroelectric ${\mathrm{Pb(Zr}}_{\mathrm{0.53}}{\mathrm{Ti}}_{\mathrm{0.47}}{\mathrm{)O}}_{\mathrm{3}}$ instead of conventional oxides as insulator gate. Because of the polarization field provided by ferroelectric and the high dielectric constant of ferroelectric insulator, the capacitance–voltage characteristics of GaN-based metal–ferroelectric–semiconductor (MFS) structures are markedly improved compared to those of other previously studied GaN MIS structures. The GaN active layer in MFS structures can reach inversion just under the bias of smaller than 5 V, which is the generally applied voltage used in semiconductor-based integrated circuits. The surface carrier concentration of the GaN layer in the MFS structure is decreased by one order compared with the background carrier concentration. The GaN MFS structures look promising for the practical application of GaN-based field effect transistors.