Gallium nitride (GaN) semiconductor devices must be fabricated using plasma etching with precise control of the etching depths and minimal plasma-induced damage on the atomic scale. A cyclic process comprising etchant adsorption and product removal may be suitable for this purpose but an understanding of the associated etching surface reactions is required. The present work examined the formation of a chlorinated layer based on Cl radical adsorption on a GaN surface in conjunction with Ar ion irradiation. This research employed beam experiments and in situ x-ray photoelectron spectroscopy. The results show that N atoms are preferentially desorbed during exposure to Ar ions to produce Ga-rich layers at depths of 0.8 and 1.1 nm at an Ar ion dosage on the order of 1016 cm−2 and ion energies of 116.0 and 212.6 eV, respectively. Subsequent exposure of the irradiated Ga-rich layer to Cl radicals removes some Ga atoms and produces a chlorinated layer over the GaN surface. This chlorinated layer has a thickness on the order of 1 nm following Cl radical dosages on the order of 1019 cm−2. This study of plasma-treated surfaces is expected to assist in developing means of controlling the etching depth during the atomic layer etching of GaN via Ar ion bombardment.

Hetero-epitaxial growth of a gallium nitride (GaN) film on an AlN(0 0 0 1) buffer layer on a sapphire(0 0 0 1) substrate was demonstrated by supplying gallium precursors and nitrogen radicals separately from two individually operated plasma sources to control the V/III supplying ratio precisely. The sources were a reactive Ar-Cl 2 -mixture plasma sputtering of a gallium target and a remote low inductance antenna (LIA) for N 2 -H 2 inductively coupled-plasma. Lateral growth of the GaN film was observed in 0.5%-Cl 2 -added Ar sputtering at a low growth temperature of 670 °C, whilst the growth mode coalesced at temperatures lower than 600 °C. With more than 2.0% of Cl 2 , no film was deposited due to etching by the reactive chlorine whenever the temperature was at 500 °C. At the growth temperature of 670 °C, crystallinity with narrow a X-ray rocking curve GaN (0 0 0 2) was obtained at the condition of 0.5% Cl 2 and 27.4% N 2 , even though the background pressure was 10 −4 Pa.

Gallium nitride films were etched at 400 °C and 20 Pa with a radio-frequency-generated Cl2–BCl3 mixed plasma. While dog-legged profiles were obtained by plasma etching using pure Cl2, straight sidewall shapes were achieved through BCl3 gas addition into the Cl2 plasma by suppressing the plasma-induced damage on the etched surface. Etching by-products containing boron on the etched surface affected the etch rate. Smooth etched profiles were obtained by controlling the redeposition of by-products of boron and chlorine compounds, particularly for substrate temperatures above 230 °C.

The growth of sputtered GaN at low temperature is strongly desired to realize the dissemination of low-cost GaN high electron mobility transistor devices for next-generation communication technology. In this work, the roles of atomic nitrogen (N)/hydrogen (H) in GaN film growth on AlN/sapphire substrates by chemically assisted dual source sputtering are studied at a low growth temperature of 600 °C under a pressure of 2 Pa using vacuum ultraviolet absorption spectroscopy. The lateral growth was strongly enhanced with an appropriate H/N flux ratio of 1.9 at a GaN growth rate of ∼1 μm h –1 . X-ray photoelectron spectroscopy measurements indicated that N removal from the grown GaN surface by atomic hydrogen promoted the migration of Ga. A smooth GaN surface was achieved at a suitable N/Ga supply ratio of 53 and a H/N ratio of 1.9 with the addition of 0.5% chlorine to the Ar sputtering gas.