Reduction of Planar Defect Density in Laterally Overgrown Cubic-GaN on Patterned GaAs(001) Substrates by MOVPE

Abstract

The metalorganic vapor phase epitaxy (MOVPE) growth of cubic-GaN (c-GaN) layers has been preformed on the [1 1 10]-stripe patterned GaAs (001) substrates. The surface morphology of the laterally overgrown layer was much improved with the formation of the flat (311)A surfaces as the growth proceeded. It is shown that the c-GaN layer thicker than 20 mm was grown on GaAs(001) substrates with the stripe direction in [1 1 10] for 90 min. Microstructure and extended defect distribution in the laterally overgrown c-GaN films have been analysed by transmission electron microscopy (TEM). It is found that the planar defect (stacking faults and twins) density drastically decreases at the region away from the substrate toward the top of the c-GaN stripe. On the other hand, the dislocations become dominant. The density of the dislocations was found to be lower than 10 8 cm --2 . These results suggest that the lateral overgrowth on [1 1 10]-stripe-patterned GaAs (001) substrates via MOVPE is an efficient method for obtaining a low planar defect density c-GaN layer.

Investigations of in situ reflectance of GaN layers grown by MOVPE on GaAs (0 0 1)

“…In order to achieve smooth and flat GaN surface and GaN/GaAs interface, several growth processes must be adequately controlled [27]. These processes include prevention of GaAs decomposition and minimizing of dislocations density that can lead to improvement of GaN crystal quality [28,29]. It is well known that, due to As element loss, uncapped GaAs decomposes when it is heated at temperature above 600°C.…”

High cubic phase purity of ELOG cubic GaN on [110] mask‐stripe‐patterned GaAs (001) substrates by MOVPE

“…It is known that for c‐GaN grown films, hexagonal phase inclusion with cubic // and hexagonal crystal orientation is probably incorporated as planar defects, including stacking faults (SFs) and twins. Because the diffraction pattern is related to these planar defects, which are typical defects observed in the meta‐stable phase c‐GaN , a large tilting from the plane is exhibited. To verify the formation of the hexagonal phase inclusion in the ELOG c‐GaN films, the X‐ray RSMs were thus performed with the incident X‐ray beams both perpendicular and parallel to the mask‐stripe direction.…”

“…These results show that the high cubic-phase purity of a c-GaN film can be achieved by using the ELOG via MOVPE with the mask-stripe direction aligned along the 110 ½ direction. As a result, this demonstrates the ability to control the structural phase transformation between cubic and hexagonal phases in the ELOG c-GaN stripes, even given the appearance of the 111 ð ÞB sidewalls [15]. It is known that the hexagonal phase inclusion is easily constructed on the 111 ð ÞB surfaces compared to that on the 111 ð ÞA [17] and 311 ð ÞA [13,15] surfaces.…”

Cubic III-nitrides: potential photonic materials

“…In the growth of c-III-N films, however, the major issue is the undesired inclusion of the hexagonal phase which degrades the whole film quality because of the metastable nature of the c-III-N. When a GaAs(001) substrate is used, it has been known that the hexagonal phase tends to be generated through stacking faults in such a way that [0001](hex)//[111](cubic) or equivalents on the {111} facets which happen to occur by thermal roughening of the substrate surface [1][2][3][4] , as illustrated in Figure 1. Thus, it is very essential to keep the initial flat surface at the beginning of the epitaxial growth on the cubic substrates.…”