MOCVD epitaxy of β -(AlxGa1−x)2O3 thin films on (010) Ga2O3 substrates and N-type doping

Abstract

(010) β-(AlxGa1−x)2O3 thin films were grown on (010) β-Ga2O3 substrates via metalorganic chemical vapor deposition with up to 40% Al incorporation by systematic tuning of the Trimethylaluminum (TMAl)/triethylgallium molar flow rate ratio and growth temperature. High crystalline quality with pure β-phase (AlxGa1−x)2O3 was achieved for films with Al composition x < 27%, while a higher Al composition induced phase segregation which was observed via X-ray diffraction spectra. Al incorporation was highly dependent on the growth temperature, chamber pressure, oxygen partial pressure, and TMAl molar flow rate. Atomic resolution scanning transmission electron microscopy (STEM) imaging demonstrated a high crystalline quality β-(Al0.15Ga0.85)2O3 film with an epitaxial interface. High resolution STEM imaging of (AlxGa1−x)2O3/Ga2O3 superlattice (SL) structures revealed superior crystalline quality for the 23% Al composition. When the Al composition reaches 40%, the SL structure maintained the β-phase, but the interfaces became rough with inhomogeneous Al distribution. N-type doping using Si in β-(AlxGa1−x)2O3 films with the Al composition up to 33.4% was demonstrated.

Probing structural and chemical evolution in (AlxGa1−x)2O3using atom probe tomography: A review

“…6, and details about this structure is reported in Ref. [38]. Machine learning in APT to study phase transformation of (Al…”

“…Experimental demonstration of Si doping in (Al x Ga 1−x ) 2 O 3 is also reported where Si incorporation was confirmed [37,38,108,109], but comprehensive understanding of the atomic-level dopant behavior with the doped (Al x Ga 1−x ) 2 O 3 films needs further effort. To characterize the n-type doping in (Al x Ga 1−x ) 2 O 3 with varying Al content, it is extremely important to accurately detect and quantify the dopant elements.…”

“…N-type doping in (Al x Ga 1−x ) 2 O 3 is in its early stage. Although several groups confirmed dopant incorporations in (Al x Ga 1−x ) 2 O 3 [37,38], a detailed understanding of dopant behavior including dopant distribution with threedimensional (3D) atomic positions within the structure, dopant segregation, and specific site occupancy is still lacking. A comprehensive study of the dopant chemistry and its influence on the electrical properties in (Al x Ga 1−x ) 2 O 3 is required for highperformance device realization since doping in wide bandgap material has been a long-standing challenge due to selfcompensation of dopants [39,40,41,42,43,44].…”

Atomic Distribution of Al and Phase Transformation in β-(AlxGa1-x)2O3

“…Hsien-Lien Huang, Jared Johnson and Jinwoo Hwang The Ohio State University, Columbus, Ohio, United States β-Ga2O3 has gained tremendous attention as a promising transparent conductive oxide, ultra-wide band material due to its unique advantages including a large band gap energy (~ 4.8eV), high breakdown voltage, and its availability as high quality bulk grown single crystals [1]. However, realizing its full potential as a semiconductor material requires the manipulation and control of its band gap, which could enable novel heterostructure designs for carrier confinement and field effect transistors or deep UV optoelectronic devices.…”

“…Recent efforts have indicated that the bandgap of β-Ga2O3 can be engineered through the incorporation of Al [2], forming β-(AlxGa1−x)2O3 with a band gap up to 8.8 eV. High crystalline quality β-(AlxGa1-x)2O3 structures with Al composition up to x=40% have been achieved using metalorganic chemical vapor deposition (MOCVD) [1] and a high mobility two-dimensional electron gas has been demonstrated to form at a β-(AlxGa1−x)2O3/Ga2O3 interface [2]. Ultimately, advancing these alloyed β-Ga2O3 epitaxial films requires the precise control of the point defects that critically influence their important properties.…”