Hydrogen Iodide (HI) Neutral Beam Etching Characteristics of InGaN and GaN for Micro-LED Fabrication.

We investigated the etching characteristics of hydrogen iodide (HI) neutral beam etching (NBE) of GaN and InGaN and compared with Cl 2 NBE. We showed the advantages of HI NBE vs Cl 2 NBE, namely: higher InGaN etch rate, better surface smoothness, and significantly reduced etching residues. Moreover, HI NBE was suppressed of yellow luminescence compared with Cl 2 plasma. InCl x is a product of Cl 2 NBE. It does not evaporate and remains on the surface as a residue, resulting in a low InGaN etching rate. We found that HI NBE has a higher reactivity with In resulting in InGaN etch rates up to 6.3 nm/min, and low activation energy for InGaN of approximately 0.015 eV, and a thinner reaction layer than Cl 2 NBE due to high volatility of In- I compounds. HI NBE resulted in smoother etching surface with a root mean square average (rms) of 2.9 nm of HI NBE than Cl 2 NBE (rms: 4.3 nm) with controlled etching residue. Moreover, the defect generation was suppressed in HI NBE vs. Cl 2 NBE, as indicated by lower yellow luminescence intensity increase after etching. Therefore, HI NBE is potentially useful for high throughput fabrication of μLEDs.