Reduction in edge dislocation density in corundum-structured α-Ga₂O₃ layers on sapphire substrates with quasi-graded α-(Al,Ga)₂O₃ buffer layers

Abstract

Efforts have been made to reduce the density of defects in corundum-structured α-Ga2O3 thin films on sapphire substrates by applying quasi-graded α-(Al x Ga1− x )2O3 buffer layers. Transmission electron microscopy images revealed that most strains were located in the α-(Al x Ga1− x )2O3 buffer layers, and that the total density of dislocations in the α-Ga2O3 thin films was successfully decreased by more than one order of magnitude compared with that without buffer layers, that is, the screw and edge dislocation densities were about 3 × 108 and 6 × 108 cm−2, respectively.

Crystal orientation dictated epitaxy of ultrawide-bandgap 5.4- to 8.6-eV α-(AlGa) 2 O 3 on m-plane sapphire

“…On the other end of the -(Al x Ga 1−x ) 2 O 3 alloy system, single-crystalline -Ga 2 O 3 films and conductive, n-type doped films are successfully grown on c-and m-plane sapphire substrates by mist chemical vapor deposition (CVD) (12,17) and halide vapor-phase epitaxy (HVPE) (24,25). -(AlGa) 2 O 3 alloys have also been grown using MBE on a-plane (0 ≤ x ≤ 1) (26), mist-CVD on c-plane (0 ≤ x ≤ 0.81) (27)(28)(29)(30), and PLD on r-plane sapphire substrates (0.92 ≤ x ≤ 1) (23). Among the growth methods, MBE and MOCVD offer the capability to maintain sharp interfaces across layers in quantum heterostructures of different alloy compositions (8,21,31,32), as well as sharply controlled doping profiles, which are problematic with HVPE or mist-CVD techniques.…”

Azimuthal Anisotropy of Rhombohedral (Corundum Phase) Heterostructures

“…The growth of (corundum phase) α ‐Ga 2 O 3 [ 1,2 ] and α ‐ alloys for buffer layers [ 3–6 ] on sapphire has gained large interest. Also, the system is interesting as barrier layer for Ga 2 O 3 and ‐based heterostructures; [ 7,8 ] the corundum phase offers the larger band offsets compared with the monoclinic phase.…”

Plastic strain relaxation and alloy instability in epitaxial corundum-phase (Al,Ga)2O3 thin films on r-plane Al2O3

“…The focus of this paper is on the rhombohedral (or trigonal) phase, also termed corundum-or α-phase. The growth of α-Ga 2 O 3 5,6 and α-(Al,Ga) 2 O 3 alloys for buffer layers [7][8][9][10] on sapphire has gained large interest. Also, the (Al,Ga) 2 O 3 -system is interesting as barrier layer for Ga 2 O 3 -and (In,Ga) 2 O 3 -based heterostructures 11,12 ; the corundum phase offers the larger band offsets compared to the monoclinic phase 13 .…”