Dry and wet etching characteristics of InN, AlN, and GaN deposited by electron cyclotron resonance metalorganic molecular beam epitaxy

Abstract

The dry etching characteristics of thin film InN, AlN, and GaN epitaxial layers deposited using metalorganic group III sources (trimethylindium, trimethylamine alane, and triethylgallium) and electron cyclotron resonance (ECR) plasma excited atomic nitrogen in a metal organic molecular beam epitaxy (MO‐MBE) chamber have been examined using CCl₂F₂/Ar, BCl₃/Ar, and CH₄/H₂/Ar discharges. In a hybrid ECR‐rf system, the Cl‐based chemistries readily etch GaN and AlN, while addition of F to the discharges dramatically reduces the etch rate of AlN. Slow, smooth etching of InN is achieved with the CH₄/H₂/Ar chemistry. Controlled rates of ∼200 Å min⁻¹ are obtained for all three materials at moderate dc biases (≤−200 V), low pressure (1 mTorr), and low microwave power (200 W). The dc bias and pressure dependence of the etching have been systematically studied. GaN films can be wet chemically etched in 30–50% NaOH solutions, AlN in HF and InN in HCl:HNO₃ solutions.