[19p-P11-1~31] 21.1 Joint Session K "Wide bandgap oxide semiconductor materials and devices"

[19p-P11-10] Preparation of flat β-Ga₂O₃(-201) for nitride growth surface and UHV observation

〇Masahiro Nakatani¹, Lei Chen¹, Arifumi Okada¹, Romuald A Ferreyra¹, Daisuke Ueda¹, Kohei Kadono¹ (1.Kyoto Inst. Tech.)

Keywords:gallium oxide, surface structure, scanning probe microscope

Since the conduction band discontinuity to that of Gallium nitride, gallium oxide is favorable to construct the vertical devices. Moreover, the atomic arrangement of oxygen of β-Ga_2 O_3 (-201) plane is close to that of Ga or N of GaN(0001). Therefore, β-Ga_2 O_3 (-201) plane has an advantage to prepare the defect-free GaN/Ga_2 O_3 interface. However, the detailed mechanism of growth has not been clarified. For atomistic study of the initial stage of growth, it is essential to perform the surface structural analysis using flat and clean substrates. In the present study, we performed high resolution observations of Ga_2 O_3 with some surface treatments, i.e., vacuum annealing and chemical etchings. For chemical etchings, phosphoric acid or an aqueous solution of potassium hydroxide were used. The surface morphologies were investigated using atomic force microscopy (AFM) and scanning tunneling microscopy (STM) in ultrahigh vacuum (UHV). In the case of vacuum annealing, color change was observed, and sometimes sample conductivity was lost. In the case of chemical etching the step-terrace structures also formed. In contrast to KOH solution, the etching was relatively uniform.