表題番号：2013A-6309
日付：2014/04/04
研究課題シリコン発光ディバイスの研究
| 研究者所属（当時） | 資格 | 氏名 | |
|---|---|---|---|
| （代表者） | 理工学術院 | 教授 | 加藤 勇 |
- 研究成果概要
- 1. Double Tubed Coaxial Line-MPCVD (DTCL-MPCVD) System
We have developed DTCL-MPCVD system. The microwave frequency is 2.45GHz. If one uses the cylindrical tube as a circular wave guide to create a microwave plasma in a discharge tube, the inside cylindrical tube diameter is to be larger than about 8cm. In this case, microwave power density is low. However there is a plasma column in the discharge tube. The plasma column in the discharge tube has large conductivity. Then we consider that the metal cylindrical tube and the plasma column construct a coaxial-line. The coaxial-line does not have the cut off frequency. One can use thinner cylindrical tube to get higher microwave energy density. In this system, the inside cylindrical tube diameter is 3cm. In the case of smaller than about 3cm, only the fundamental mode of the coaxial-line can propagate. Then this discharge system is named the “coaxial-line-type”.
Two kinds of gas are separately fed through an outer discharge tube which is the fused quartz and is 1.3cm inside diameter and an inner tube which is 0.6cm outside diameter. Then it is named the “double-tubed”.
The plasma flows into the deposition chamber and its electron temperature decreases rapidly. There is no microwave energy in the deposition chamber because the discharge tube end is capped by the plasma. Therefore, the plasma in the deposition chamber becomes the “spatial” after-glow plasma in the deposition chamber.
If the mixed gas (the discharge gas and the material gas) flows into the discharge tube, some materials deposit on the inside wall of the discharge tube. The microwave discharge is stopped sooner or later because the window which the electric energy enters is closed.
This system has many merits. The details are reported in the reference [3].
2. Photoluminescence(PL) from the Si nano-Crystal Films
To develop Si light source, many kinds of Si nano-crystal films are fabricated using H2, N2 and Ar gas as the discharge gas, and silane and TEOS gas as the material gas.
In the case of H2, Ar and silane gas, Si nano-crystal is varied in a-Si:H film which does not emit PL because the a-Si:H absorbs light. But the film emits PL after the thermal oxidation, because the a-Si:H changes to SiO2 [1]. In the case of N2 and silane gas, the film emits PL without thermal oxidation, because the film is Si3N4 which is a transparent material. The light emission is obtained without oxygen (no siloxane) [2].
3. PL Wavelength and Carbon Ratio
Using TEOS gas, the spectra shift to blue side, compared with the case of silane gas, because the film includes carbon. After the thermal oxidation, the spectra shift to red side. The result of composition analysis shows that carbon decreases after the thermal oxidation. It means that carbon is burned out. However, the size of Si nano-crystal is also decreasing at the same time. And it shifts blue side again. The details are reported with the film structures, spectra and composition analyses [3].
REFERENCES
[1] T. Tachibana, H. Sakamoto, I. Kato, ADVANCES IN APPLIED PLASMA SCIENCE, Vol.6, 2007, pp. 1-2.
[2] T. Funatsu, I. Kato, ADVANCES IN APPLIED PLASMA SCIENCE, Vol.8, 2011, pp. 173-174.
[3] I. Kato, J. Makino, E. Takeda, A. Shiozawa, ADVANCES IN APPLIED PLASMA SCIENCE, Vol. 9, 2013 pp. 63-64.