HETEROEPITAXY BETWEEN LAYERED SEMICONDUCTORS GASE AND INSE

The initial stage of heteroepitaxy of GaSe on InSe, and InSe on GaSe has been studied by means of AES (Auger electron spectroscopy), LEELS (low-energy electron-loss spectroscopy) and XPS (X-ray photoelectron spectroscopy). GaSe(InSe) was deposited onto the substrate by using a W filament. The growth mode was determined by measuring the decrease in the AES signal intensity from the substrate upon deposition, which reveals that GaSe deposited on InSe (or InSe on GaSe) grows layer-by-layer with unit thickness of the primitive layer consisting of four atomic planes in the sequence Se-M-M-Se (M = Ga, In). The crystal quality of the grown layer was characterized by LEELS. The results indicate that the grown layers of about two primitive layers deposited at elevated temperature (≈300°C) have the same crystal quality as the bulk crystal, in spite of the large lattice mismatch of about 7% between GaSe and InSe. The valence band discontinuity between GaSe and InSe estimated by XPS was less than 0.1 eV, and the conduction band discontinuity is thus about 0.7 eV due to the band gap difference between the two crystals. © 1989.