Current collapse-free i-GaN∕AlGaN∕GaN high-electron-mobility transistors with and without surface passivation

Abstract

Drain current $\left(I_D\right)$ collapse-free $i\text{-}\mathrm{GaN}∕\mathrm{AlGaN}∕\mathrm{GaN}$ high-electron-mobility transistors (HEMTs) with and without surface passivation (electron-beam evaporated ${\mathrm{SiO}}_2$ ) were demonstrated using dc and pulsed $\left(120\mathrm{Hz}\right)$ $I_{DS}–V_{DS}$ characteristics up to the drain supply voltage of $40\mathrm{V}$ . The observation of small $I_D$ transients and negligibly small hysteresis widths with small white light illumination effects on both passivated and unpassivated $i\text{-}\mathrm{GaN}∕\mathrm{AlGaN}∕\mathrm{GaN}$ HEMTs confirms the suppression of collapse related traps. Three and two thermally activated trap levels were observed in passivated ($+0.395$ , $-0.079$ , and $-0.949\mathrm{eV}$ ) and unpassivated ($-0.066$ and $-0.368\mathrm{eV}$ )$\mathrm{AlGaN}∕\mathrm{GaN}$ HEMTs, respectively. However, $i\text{-}\mathrm{GaN}∕\mathrm{AlGaN}∕\mathrm{GaN}$ HEMTs with and without surface passivation exhibited only one trap level at $-0.161\mathrm{eV}$ . These results show that the addition of thin cap layer $i\text{-}\mathrm{GaN}$ screens the collapse-related surface states/traps from channel.