Dislocation reduction through nucleation and growth selectivity of metal-organic chemical vapor deposition GaN

Abstract

A novel serpentine channel structure is used to mask the sapphire substrate for the epitaxial growth of dislocation-free GaN. Compared to the existing epitaxial lateral overgrowth methods, the main advantages of this novel technique are: (a) one-step epitaxial growth; (b) up to 4 times wider defect-free regions; and (c) the as-grown GaN film can be transferred easily to any type of substrate. TEM, etch pits and cathodoluminescence experiments are conducted to characterize the quality of as-grown GaN. The results show that the average etch-pit density in the yet-to-beoptimized GaN epi-layers is about 4 Â 10 5 cm À2. The underlying physics of selective nucleation and growth is investigated using the finite element method (COMSOL). It is concluded that the proximity effect dominates the selective growth of GaN on the serpentine channel structure masked sapphire. This novel technique is a promising candidate for the growth of high quality III-nitride and the subsequent high-performance device fabrication including high brightness LED, laser diodes, and high-power, high-efficiency transistors. V

Dislocation Reduction and Stress Relaxation of GaN and InGaN Multiple Quantum Wells with Improved Performance via Serpentine Channel Patterned Mask

“…It clearly confirms that the TDs can be effectively reduced by the serpentine channel patterned mask. GaN template grown on SCPSS has an average TDD of ∼3–5 × 10 5 cm –2 , which is close to the level of freestanding GaN homoepitaxy, PE, and FACELO, ,, and approximately 1 order of magnitude less than most of the other ELOG methods. , The EPD estimated here using molten KOH is consistent with the etch-pit result after mixture solution of H 2 SO 4 and H 3 PO 4 etching at 160 °C in our previous work (∼4–7 × 10 5 cm –2 ). , Hence, within a certain tolerance, wing and window regions can be used as a whole for high-quality device fabrication, which accounts for about 80% of the total area.…”

“…1,9 The EPD estimated here using molten KOH is consistent with the etch-pit result after mixture solution of H 2 SO 4 and H 3 PO 4 etching at 160 °C in our previous work (∼4−7 × 10 5 cm −2 ). 28,29 Hence, within a certain tolerance, wing and window regions can be used as a whole for highquality device fabrication, which accounts for about 80% of the total area.…”

Effects of InGaN-interlayer on closed stripes of GaN grown by serpentine channel patterned sapphire substrate

“…The internal quantum efficiency (IQE) of multi-quantum wells (MQWs) grown by serpentine channel patterned sapphire substrates (SCPSS) was 52% higher than that of conventionally developed counterparts [8]. Additionally, such single-step growth consumes lower energy and is conveniently transferable to another substrate [7]. It was observed that in the case of coalescence growth, the growth fronts meet at mid of two adjacent windows and produce defective areas called meetingfronts [18].…”

“…Despite all these benefits, the further applications of GaN-based devices are hindered due to the lack of native substrates. The growth of these devices on heterogeneous substrates, such as sapphire, SiC, and Si is a technical challenge [7] as large lattice and thermal mismatch between GaN and such conventional substrates produce huge numbers of threading dislocations (TDs) [8].…”

“…However, in region B and region C, TDs have only horizontal configurations. Such horizontal TDs (HDs) do not intersect the surface of GaN-based devices so; these TDs do not threaten the device performance [7]. In previous cases, TDs react with each other's and make dislocation loops while, in some cases, TDs terminate inside the window area.…”