この研究課題のドキュメント
| 1986年 | |
|---|---|
| 1987年 |
研究課題基本情報（最新年度）
研究期間
1986年度〜1987年度研究分野
審査区分
研究種目
一般研究(B)
研究機関
東京農工大学
配分額
- 総額：6700千円
- 1986年度：4900千円 (直接経費：4900千円)
- 1987年度：1800千円 (直接経費：1800千円)
研究概要（最新報告）
1.半導体中の深い準位の電子状態のサーベイ
半導体中の深い準位特に遷移元素不純物のエネルギー状態の実験および理論研究の現状について文献調査を行い, 現在までに解明されていることと, 未解明のことを整理した.
2.磁気円二色性測定装置の整備, 調整
本研究費で購入した部品を既存設備等と組合せ磁気円二色性スペクトル測定装置を組立て, 調整を行った. 測定波長範囲は0.4〜2.4μm, 温度範囲20〜300K, 磁界0〜1.3Tである. MCDの感度は△αl=10^<-5>程度が得られた.
3.試料の準備
HB法で作製されたCr添加半絶縁性GaAsの5mm厚2インチウェハーから10×10mm^2の試料が切り出され, 研磨された. またLEC法無添加半絶縁性GaAsについても10×10×5mm^3の試料が準備された. In添加GaAsについても8×8×3mm^3の試料が作製され, As雰囲気処理と, Cr熱拡散処理が行われた. InP.Feについては10×10×0.5mm^3の試料が用意された.
4.磁気円二色性の実験と解析
測定した試料はいずれもサブギャップに吸収帯を示し, その吸収帯のエネルギー範囲でMCDの構造を示した. GaAs:Crについて, 価電子帯の波動関数を考慮したMCDスペクトルの形状の解析を理論計算に基いて行った. 得られたフィッティングは満足すべきものあったが, パラメータの意味づけに若干の問題が見られ, 理論の修正の必要が明らかにされた.
5.結晶工学的評価手段としての磁気円二色性
MCDスペクトルは熱処理, Cr添加等により大きく変化し, 結晶欠陥に敏感であることがわかった. また試料のウエハー内の位置によってもMCDに変化が見られ結晶工学的評価に用いうる.
(1)Survery of electronic structures associated with the deep levels in semiconductors
Experimental and theoretical studies concerning the electronic structures of deep impurity levels in semiconductors were surveyed with particular reference to those introduced by transition atom impurities.
(2)Layout, setup and abjusting of apparatus for magneto-circular dichroism spectrum
By combining optical elements purchased by this grant-in-aid, apparatus for the measurement of magneto-circular dichroism spectrum in the near-infrared region was constructed. This apparatus consists of a halogen-tungsten light source, a monochromator, an optical system with ellipsoidal mirrors, a polarizer, a piezo-birefringent modulator, an electromagnet with a perforation through its pole-pieces, a cryostat with helium a refrigerator and a semiconductor photocell for infrared detoction. This apparatus is equipped with an electronic system including two lockin-amplifiers and a microprocessorbased data-acquisition system. This apparatus is capable of measuring the MCD for 0.4- 2.4um with magnetic field up to 13kG between temperatures from 20K to 300K.
(3)Preparation of specimens
Chromium-doped semi-insulating GaAs wafers with different concentration of chromium made by the horizontai Bridgmann(HB)-method, an undoped semi-insulating GaAs wafer grown by liquid encapsulated Czochralski(LEC) technique, indium-doped dislocation-free GaAs ingots with different conductivity types(p,i,n) and LEC-grown InP wafers doped with iron were cut and polished to serve as specimens for the measurement of MCD. Heat treatment in arsemic atmosphere or chromium diffusion was also carried out.
(4)Measurement and theoretical analysis of MCD spectra
All specimens measured showed MCD structures below the fundamental energy gap characteristic to the nature of the crystal. Among these spectra, MCD spectrum associated with the photoionization transition in HB-grown GaAs:Cr was analyzed in terms of the quantum defect model assuming the transition occurs from spin-orbit-split valence bands to Cr-related deep states. The calculated spectrum fit to the experimental one was satisfactory with the energy threshold 0.89eV and spin-orbit parameter of 0.2eV. The latter value is too small compared with that known for valence band splitting; i.e. 0.35eV. This suggests that a modification of the theory is necessary.
(5)MCD as a crystal evaluation technique
It was found that MCD spectrum is very sensitive to crystallinity; for example the spectral shape changes drastically by heat treatment. Therefore, it becomes clear that the technique can be used as an evaluation method for crystal properties if we can classify MCD data for crystals with different treatments.
このページのURI
http://kaken.nii.ac.jp/ja/p/61460061