Fig. 1. AFM diagrams of (a) sample 1, (b) sample 2, (c) sample 3, (d) sample 4, and (e) GaSb substrate; (f) root mean square roughness

Fig. 2. XPS diagrams of Ga 3d energy levels of different samples. (a) Sample 1; (b) sample 2; (c) sample 3; (d) sample 4

Fig. 3. Peak area of Ga—O bond and peak area ratio between Ga—N and Ga—O bonds

Fig. 4. XPS energy spectra of Ga 3d of different samples. (a) Sample 1; (b) sample 2; (c) sample 3; (d) sample 4

Fig. 5. Peak area of Sb—O bond and peak area ratio among Sb—O bonds of different samples and substrate

Fig. 6. (a) PL spectra of samples at room temperature under different etching cycles and (b) corresponding luminous intensities and FWHM