Exploratory phase stabilization in heteroepitaxial gallium oxide films by pulsed laser deposition

Gallium oxide (Ga 2 O 3 ) is featured by various types of polymorphs that exhibit distinct properties for a broad range of applications. Selective stabilization of distinct Ga 2 O 3 polymorphs is highly desired, but is usually limited by impurity phase formation. Here we report the controlled growth of metastable gallium oxide films by pulsed laser deposition (PLD), and explore a comprehensive phase evolution picture tuned by key synthesis parameters, substrate orientations, and extrinsic tin (Sn) dopants. We demonstrate the stabilization of both undoped and Sn-doped α -Ga 2 O 3 films by selecting a-plane sapphire substrates, and find that Sn dopants can largely broaden the growth window of α -Ga 2 O 3 . Besides, Sn-doped ε -Ga 2 O 3 is more favored than β -Ga 2 O 3 to be stabilized on c-plane substrates, and the oxygen pressure is the critical factor to dictate the ε -Ga 2 O 3 formation. The structural impact on the thermal transport among these metastable Ga 2 O 3 films is investigated, which shows a maximum value of 5.66 Wm -1 K -1 in α -Ga 2 O 3 and a minimum value of 1.04 Wm -1 K -1 in amorphous Ga 2 O 3 . The native defects of these phases are sensitive to the Sn doping, which exhibits a distinct response for deep ultraviolet photodetection. This study establishes a synthesis guideline of metastable Ga 2 O 3 polymorphs by PLD and provides insights into selective phase stabilization of transition metal oxides with various crystal phases. • A comprehensive picture of the Ga 2 O 3 phase evolution has been established by pulsed laser deposition. • Sn dopants can largely broaden the growth window of both ε- and α-Ga 2 O 3 and suppress intrinsic defects. • The thermal conductivity of β-, ε-, α-Ga 2 O 3 and amorphous films are measured by time domain thermoreflectance.