Control of Crystal Structure of Ga₂O₃ on Sapphire Substrate by Introduction of α‐(Al_xGa_1−x)₂O₃ Buffer Layer

Abstract

An annealed α‐(Al0.4Ga0.6)2O3 buffer layer is introduced to achieve either α‐Ga2O3 or ϵ‐Ga2O3 growth on sapphire substrates, depending on the growth temperature, using the mist chemical vapor deposition method. Transmission electron microscopy reveals that the epitaxial relationship between ϵ‐Ga2O3 and the α‐(Al0.4Ga0.6)2O3 buffer layer is ϵ‐Ga2O3 [101¯0] || α‐(Al0.4Ga0.6)2O3 [112¯0], and the two hexagonal lattices are consequently rotated in the ab plane by 30° with respect to each other. The lattice mismatch between the buffer layer and ϵ‐Ga2O3 is 1.2%, while that between the buffer layer and α‐Ga2O3 is 2.2%. When the growth temperature is below 600 °C, ϵ‐Ga2O3, which had the smaller lattice mismatch, is produced. On the other hand, higher temperature leads to a longer diffusion length, and atoms reach the step edges. Therefore α‐Ga2O3, which has the same structure as the buffer layer, is grown along the step edges above 600 °C. As a result, ϵ‐Ga2O3 and α‐Ga2O3 grow below and above 600 °C, respectively.

First-Principles Studies for Electronic Structure and Optical Properties of Strontium Doped β-Ga2O3

“…This UWBG material has excellent heat thermal stability utilized in power electronics applications [9,10]. Perhaps, history of the monoclinic β-Ga 2 O 3 can be traced back in the recent past few years due to its stable properties that eventually draw scientists' profound interest [11][12][13].…”

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 .…”