1997 Fiscal Year Final Research Report Summary
Magnetic Field induced Metal Nonmetal Transition for Semiconductors by Use of Zeeman Magneto-Spectroscopy
| Project/Area Number |
08640419
|
|---|
| Research Category |
Grant-in-Aid for Scientific Research (C)
|
| Allocation Type | Single-year Grants |
|---|
| Section | 一般 |
|---|
| Research Field |
固体物性Ⅰ(光物性・半導体・誘電体)
|
|---|
| Research Institution | Osaka University |
|---|
Principal Investigator |
KOBORI Hiromi Graduate School of Science, Osaka University, Research Assistant, 大学院・理学研究科, 助手 (90202069)
|
|---|
| Co-Investigator(Kenkyū-buntansha) |
FUJII Kenichi Graduate School of Science, Osaka University, Research Assistant, 大学院・理学研究科, 助手 (10189988)
NAKATA Hiroyasu Graduate School of Science, Osaka University, Associate Professor, 大学院・理学研究科, 助教授 (60116069)
OHYAMA Tyuzi Graduate School of Science, Osaka University, Professor, 大学院・理学研究科, 教授 (40029715)
|
|---|
| Project Period (FY) |
1996 – 1997
|
| Keywords | Metal-Nonmetal / Magnetic / Semiconductor / Zeeman / Donor / Thomas-Fermi / Screening / Variational |
|---|
| Research Abstract |
To study the magnetic field induced metal-nonmetal transition for semiconductors by use of Zeeman magneto-spectroscopy, we have employed n-GaAs, which has a isotropic effective mass of the conduction band and can be fitted to the effective mass approximation. The critical donor concentration of the metal-nonmetal transition for n-GaAs is 1.6*10^<16>cm^<-3>. We have prepared more than 10 kinds of epitaxially grown n-GaAs samples of which concentration is between 10^<14>cm^<-3> and 10^<18>cm^<-3>. Zeeman magneto-absorption of donors for ls*2P_<+1> transition has been investigated in details as the functions of donor concentration, magnetic field and temperature. When the Zeeman magneto-absorption can be observed, the semiconductor is in the nonmetallic phase, and vice versa. We have observed the striking line-broadening of the Zeeman magneto-absorption with increasing the donor concentration and the disappearance of that above the critical donor concentration. Furthermore, we have observed the considerable narrowing of the Zeeman magneto-absorption with increasing the magnetic field. The shift of the critical donor concentration to a higher one and the magnetic field induced metal-nonmetal transition have been recognized on the application of the magnetic field. To explain our experimental results quantitatively, we carried out variational calculations within the Thomas-Fermi approximation and evaluated the critical donor concentration of the metal-nonmetal transition. Employing the reliable variational wavefunctions, we firstly calculated energy levels of a donor in a magnetic field without the screening and obtained the good results. We secondly carried out numerical calculations with screening and thirdly extended our calculations to the case in the presence of the magnetic field and the screening.
|
