(Invited) Fabrication of AlGaN/InGaN/GaN Quantum Wires for Electronic and Optoelectronic Applications

Abstract

AlGaInN epi structures are used for manufacturing white LEDs, UV, blue and green laser diodes (LD) and high-power/high-frequency transistors. In this work, we will show our proprietary and patented technology of lateral patterning in which we fabricate GaN substrates with locally variable off-cut (variable atomic step width). Such substrates are used for InGaN and AlGaN growth of 3-dimensional epi structures. The GaN off-cut influences a number of AlGaInN characteristics: Indium incorporation (smaller for a higher off-cut), Ga and N vacancies concentration, critical conditions for relaxation, decomposition rate, and some others. Therefore, using the GaN substrates after such lateral patterning, we may fabricate nano-wires which would be used for electronic device manufacturing. Unfortunately, AlGaInN epitaxial layers contain a large number of defects (dislocations, trench defects, In-clusters, and some others) which disturb the step-flow. We will show a comparison of results obtained using different GaN crystals: thick layers on sapphire and SiC (dislocation density higher than 108 cm-2), bulk crystals grown by various methods having dislocation density between 107 cm-2 and 104 cm-2. Then, we will present how the growth conditions (temperature, pressure, flows of reactants, presence of hydrogen in the carrier gas) influence the nanowire formation. One of the big issues in nitride technology is InGaN decomposition during the p-type growth at temperatures higher than those used for InGaN growth. Therefore, part of the presentation will be devoted to that issue, in particular, how lateral patterning may influence this decomposition.