Defect structure in heteroepitaxial semipolar (11\bar {2} 2 ) (Ga, Al)N

Abstract

The defect structures in semipolar (1122)-GaN, AlN layers grown on m-sapphire by metal organic vapor phase epitaxy (MOVPE) and molecular beam epitaxy (MBE) are characterized by transmission electron microscopy. The epitaxial relationships are identified as [1010](GaN) || [1120]sap and [1213](GaN) || [0001]sap. Defects are identified as mostly partial dislocations, I1-basal and prismatic stacking faults. The density of dislocations is of the order of 5.5 × 10(9) cm(-2). They are Frank-Shockley partial dislocations with b = 1/6<2023> (90%), Shockley partial dislocations with b = 1/3<1010> (8%) and perfect dislocations of a-type with b = 1/3<1120> (2%). This is in contrast with the growth in c- or a-orientations, where the large majority of extended defects consists of perfect dislocations. Upon MBE regrowth of GaN on MOVPE GaN, no additional defects are generated, although the defects in the substrate propagate through the overgrown layer. However, in the case of MBE deposition of AlN on MOVPE GaN, new threading dislocations of the type b = 1/3<1123> are generated taking stepped and curved structures along their lines.

Defect evolution and interplay in n-type InN

“…1 ) of stacking faults was revealed for WB conditions 8 with g ¼ 10-10 (not shown here). In the irradiated InN film, earlier TEM results 9 showed irradiationinduced formation dislocation loops in addition to a significant density of planar defects introduced during growth.…”

Imaging basal plane stacking faults and dislocations in (11-22) GaN using electron channelling contrast imaging

“…Stacking faults (SFs) in the basal plane with the displacement vectors R ¼ 1/3 h1-100i (I 1 type), 1/6 h20-23i (I 2 type), and 1/2 h0001i (E type) as well as in prismatic planes with R ¼ 1/2 h 1-101i and 1/6 h 20-23i are also observed. 32 In the case of semi-polar based nitride heterostructures, misfit dislocations of the edge type with b ¼ 1/ 3 h2-1-13i, formed at heterointerfaces, have also been reported recently. 33 The majority of reported BSFs are I 1 type, and the associated partial dislocations (PDs) are of the Frank-Shockley type with b ¼ 1/6 h20-23i.…”

“…32 But in the case of semi-polar nitrides, in addition to perfect TDs, Shockley partials of b ¼ 1/3 h1-100i, Frank partials of b ¼ 1/2 h0001i, and Frank-Shockley partials of b ¼ 1/ 6 h20-23i have also been reported. Stacking faults (SFs) in the basal plane with the displacement vectors R ¼ 1/3 h1-100i (I 1 type), 1/6 h20-23i (I 2 type), and 1/2 h0001i (E type) as well as in prismatic planes with R ¼ 1/2 h 1-101i and 1/6 h 20-23i are also observed.…”

Semipolar (11–22) AlN Grown on m-Plane Sapphire by Flow-Rate Modulation Epitaxy for Vacuum-Ultraviolet Photodetection

“…Semipolar (11–22) orientation of III-nitride material crystallizing in the wurtzite structure is predicted to have almost no polarization field by numerical calculations , and has attracted increasing attention. Generally, semipolar (11–22) AlN films are grown on m -plane sapphire by plasma-assisted molecular beam epitaxy and metal–organic chemical vapor deposition (MOCVD) due to the lack of bulk substrates. − However, these films typically contain the high defect densities due to the lattice and thermal expansion coefficient mismatch between the AlN epitaxial layer and sapphire, including basal stack faults (BSFs, ∼10 5 cm –1 ) and their associated partial dislocations (∼10 10 cm –2 ), along with lower densities of prismatic stack faults (PSFs, ∼10 2 cm –1 ) . Some methods have been tried to reduce the defect densities of semipolar (11–22) AlN materials, such as Ga-surfactant-assisted growth and high temperature annealing (HTA). , These methods are effective to improve the crystalline quality to some degree.…”

“…19−23 However, these films typically contain the high defect densities due to the lattice and thermal expansion coefficient mismatch between the AlN epitaxial layer and sapphire, including basal stack faults (BSFs, ∼10 5 cm −1 ) and their associated partial dislocations (∼10 10 cm −2 ), along with lower densities of prismatic stack faults (PSFs, ∼10 2 cm −1 ). 24 Some methods have been tried to reduce the defect densities of semipolar (11−22) AlN materials, such as Ga-surfactantassisted growth and high temperature annealing (HTA). 25,26 These methods are effective to improve the crystalline quality to some degree.…”