|Budget Amount *help
¥2,500,000 (Direct Cost : ¥2,500,000)
Fiscal Year 2000 : ¥700,000 (Direct Cost : ¥700,000)
Fiscal Year 1999 : ¥700,000 (Direct Cost : ¥700,000)
Fiscal Year 1998 : ¥1,100,000 (Direct Cost : ¥1,100,000)
We have clarified formation dynamics and electronic properties of heterovalent vacancy-contained interfaces as follows, by using the first-principles calculations and the crystal growth simulations.
1. Development of crystal growth simulator ; Monte Carlo crystal-growth simulations are developed, which are based on the first-principles calculations and take into account the four coordination of atoms, the surface dimer formation, the inter-bond transfer of excess charge, the long-range atom diffusion and the strain effects.
2. ZnSe/GaAs (110) and (001) interfaces ; Due to the relaxation of charge mismatch, the atomically sharp interface is easily formed at the (110) nonpolar interface. On the other hand, we found for the (001) interface that (1) the simultaneous supply of Zn and Se atoms often produces the Se antisites which induce vacancy defects and stacking faults, (2) the initial supply of only Zn atoms extinguishes such antisites, (3) the initial supply of Se promotes the As evapola
tion and produces GaSe layers having rough surfaces. It was proved that all these results originate from the heterovalency between GaAs and ZnSe compounds and well explain the observations.
3. ZnO/GaN (0001) interfaces ; At the initial growth, the interface excess charge promotes the growth by moving to the surface, while at the later stage it is strongly localized at the interface and has no effects on the growth. The resulting interface has type-II offset.
4. Vacancy compounds ; We showed that the vacancy-layered wurtzite In_2Se_3, which has large anisotropy around the absorption gap, grows along (111) with three period to relax the strain, the vacancy ternary compounds such as CdGa_2Se_4 show the large band-gap variation depending on the vacancy ordering, and the vacancy arrangement is easily observed by the Raman scattering experiments.
5. Other interfaces ; We clarified that the growth of InAs wetting layers on GaAs (001) promotes cation mixing, the reflectance difference spectra of Si (001) oscillate during the oxidation, and the limitting process by Cl to etch the Si (111) surface is not the diffusion but the desorption. Less