Trap and 1/f-noise effects at the surface and core of GaN nanowire gate-all-around FET structure

Abstract

Using capacitance, conductance and noise measurements, we investigate the trapping behavior at the surface and in the core of triangular-shaped one-dimensional (1D) array of GaN nanowire gate-all-around field effect transistor (GAA FET), fabricated via a top-down process. The surface traps in such a low dimensional device play a crucial role in determining the device performance. The estimated surface trap density rapidly decreases with increasing frequency, ranging from 6.07 x 10(12) cm(-2)eV(-1) at 1 kHz to 1.90 x 10(11) cm(-2)eV(-1) at 1 MHz, respectively. The noise results reveal that the power spectral density increases with gate voltage and clearly exhibits 1/f-noise signature in the accumulation region (V-gs > V-th = 3.4 V) for all frquencies. In the surface depletion region (1.5 V < V-gs < V-th), the device is governed by 1/f at lower frequencies and 1/f(2) noise at frequencies higher than 5 kHz. The 1/f(2) noise characteristics is attributed to additional generation-recombination (G-R), mostly caused by the electron trapping/detrapping process through deep traps located in the surface depletion region of the nanowire. The cutoff frequency for the 1/f(2) noise characteristics further shifts to lower frequency of 10(2)-10(3) Hz when the device operates in deep-subthreshold region (V-gs < 1.5 V). In this regime, the electron trapping/detrapping process through deep traps expands into the totally depleted nanowire core and the G-R noise prevails in the entire nanowire channel.