Boron trichloride plasma treatment effect on ohmic contact resistance formed on GaN-based epitaxial structure

A BCl3 plasma treatment effect on GaN surface and reduction of ohmic contact resistance in GaN/AlGaN epitaxial structure with a GaN cap layer has been studied. The BCl3 plasma treatment was carried out by an inductively coupled plasma reactive ion etching (ICP RIE) system under conditions of low discharge power with zero external bias controlling power to prevent any recess etching of the GaN cap layer. The measured average contact resistances with and without plasma treatment were 1.8×10-5 and 1.05×10-5 Ω·cm2 respectively. To study the BCl3 plasma treatment effect on GaN surface and explain the increasing of contact resistance, the elemental composition of GaN surface was measured using x-ray photoelectron spectroscopy. It was found that a Bx-Cly layer covered the GaN surface after the BCl3 plasma treatment. This can indicate that ion bombardment from plasma is inefficient to prevent deposition of BClx radicals on the GaN cap layer surface and subsequent formation of the Bx-Cly layer which is responsible for increase of ohmic contact resistance after the BCl3 plasma treatment.