Effects of inductively coupled plasma conditions on the etch properties of GaN and ohmic contact formations

In this study, n-GaN was etched using inductively coupled Cl2/H2 plasmas and the effects of plasma conditions on the etch properties, surface composition and ohmic contact formation were investigated as a function of gas composition using OES (optical emission spectroscopy), SEM (scanning electron microscope), XPS (X-ray photoelectron spectroscopy), AES (Auger electron spectroscopy) and TLM (transmission line method). The addition of hydrogen to Cl2 plasma decreased GaN etch rate and changed the surface composition from Ga-rich to N-rich. Etched profiles were near vertical with a smooth sidewall, however, the pure Cl2 case showed the most anisotropic etch profile. Specific contact resistivity was increased with increasing hydrogen percent in Cl2/H2, however, most of contact resistivities of the contacts fabricated on the GaN etched with Cl2/H2 (≤75% H2) were less than those fabricated on the non-etched GaN.