Effect of dry etching conditions on surface morphology and optical properties of GaN films in chlorine-based inductively coupled plasmas

Dry etching of undoped, n- and p-type GaN films has been carried out in a planar type inductively coupled plasma (ICP) system. The effect of etching conditions on surface morphology and optical properties of GaN films etched in Cl-2/Ar discharges was studied. All the GaN films showed overall similar etching behavior at 700 W ICP, 150 W rf, 40 mTorr, and 25% Cl-2. The surface roughness was relatively independent of the rf power up to 150 W, resulting in quite smooth morphology (root-mean-square roughness 1.1-1.3 nm), while etching at higher chuck powers (> 200W) produced rougher surfaces due to increased ion bombardment. The lattice disorder and point defect density were lower during the ICP etching compared with reactive ion etching. The intensity of the band edge peak of as-grown n-GaN was decreased after the ICP etching, and the extent of intensity decrease was inversely proportional to the applied chuck power. By contrast, the as-grown p-GaN showed a weak intensity of band edge emission, but the peak shifted to 460 nm after ICP etching with substantial increase in photoluminescence intensity. (C) 2001 American Vacuum Society.