2024/03/03 更新

写真a

ツカサキ タカシ
塚崎 貴司
所属
理工学術院 先進理工学部
職名
助教
学位
博士(工学) ( 2022年03月 早稲田大学 )

経歴

  • 2022年04月
    -
    継続中

    早稲田大学   先進理工学部 電気・情報生命工学科   助教

学歴

  • 2019年04月
    -
    2022年03月

    早稲田大学   パワー・エネルギー・プロフェッショナル育成プログラム  

  • 2017年04月
    -
    2022年03月

    早稲田大学   大学院 先進理工学研究科   電気・情報生命専攻  

  • 2013年04月
    -
    2017年03月

    早稲田大学   先進理工学部   電気・情報生命工学科  

所属学協会

  • 2017年06月
    -
    継続中

    応用物理学会

研究分野

  • 結晶工学

研究キーワード

  • Ⅲ-Ⅴ族化合物半導体、窒素添加混晶、結晶成長、半導体デバイス、分子線エピタキシー

 

論文

  • Recombination mechanism of heavily Be-doped GaAsN by time-resolved photoluminescence

    Takashi Tsukasaki, Hisashi Sumikura, Takuma Fujimoto, Miki Fujita, Toshiki Makimoto

    Journal of Vacuum Science & Technology A   41 ( 5 ) 052702  2023年07月  [査読有り]

    担当区分:筆頭著者, 責任著者

     概要を見る

    The optical properties of GaAsN system alloys have not been clarified, particularly for the localized level around the bottom of the conduction band induced by nitrogen atoms. Herein, the recombination mechanism is systematically investigated for heavily Be-doped p-type GaAsN using both continuous-wave (CW) and time-resolved (TR) photoluminescence (PL) characteristics, which is expected to be applied to devices such as a p+-n+ tunnel diode inserted into a multijunction solar cell composed of GaAs system alloys and as the base layer of a heterojunction bipolar transistor. The S-shape characteristic weakened with increasing hole concentration (p) in the CW-PL spectra of Be-doped GaAsN. Both short and long lifetimes were evaluated using TR-PL decay curves. Specifically, the long lifetime was distributed between 0.7 and 1 ns independent of temperature and p. This long lifetime corresponds to radiative recombination lifetime from a localized level, supporting that a localized level is formed in Be-doped GaAsN despite high p on the order of 1019 cm−3. Electrons are tightly bound at a localized level, equivalent to this long lifetime, whereas the electron lifetime decreases with increasing p, resulting in the S-shape characteristic vanishing in the temperature dependence of the CW-PL spectra for ultraheavily Be-doped GaAsN with p of 5 × 1019 cm−3. Moreover, this S-shape characteristic vanished in the temperature dependence of TR-PL spectra for moderately Be-doped GaAsN with p of 8 × 1018 cm−3, indicating that the density of states is limited for a localized level.

    DOI

    Scopus

  • Electrical properties of heavily Si-doped GaAsN after annealing

    Takashi Tsukasaki, Naoki Mochida, Miki Fujita, Toshiki Makimoto

    Physica B: Condensed Matter   625  2022年01月  [査読有り]

    担当区分:筆頭著者, 責任著者

     概要を見る

    In this study, electron traps in dilute GaAsN are investigated using the temperature dependence of electron concentration (n) and mobility (μe) for annealed heavily Si-doped GaAsN. The temperature dependence of n and μe depends on the annealing temperature, indicating that electrons are excited to the conduction band only from deep electron traps for heavily Si-doped GaAsN annealed at 580 °C. However, they are excited to the conduction band from both the deep electron traps and the shallow Si donor level for heavily Si-doped GaAsN annealed at 550 °C. The depth of the deep electron traps from the bottom of the conduction band for heavily Si-doped GaAsN annealed at 550 °C is almost equal to heavily Si-doped GaAsN annealed at 580 °C. The results demonstrate that these deep electron traps are inherent in dilute GaAsN because similar deep electron traps are also observed for the as-grown Si-doped GaAsN.

    DOI

    Scopus

    1
    被引用数
    (Scopus)
  • Correction: Photoluminescence Mechanism in Heavily Si-Doped GaAsN (Crystal Research and Technology, (2021), 56, 3, (2000143), 10.1002/crat.202000143)

    Takashi Tsukasaki, Ren Hiyoshi, Miki Fujita, Toshiki Makimoto

    Crystal Research and Technology   56 ( 11 )  2021年11月  [査読有り]

    担当区分:筆頭著者, 責任著者

     概要を見る

    In the originally published article, the following values were presented incorrectly: 1) The values of the Si impurity concentration ([Si]) and the electron concentration (n) are slightly erroneous for the heavily Si-doped GaAsN, which are described as 6 × 1019 cm–3 and 9 × 1018 cm–3, respectively. The correct values of them are 2 × 1019 cm–3 and 6 × 1018 cm–3, respectively. Figure 1 and 2 with the correct values are presented below. 2) The value of n is applied for the evaluation of electron effective mass (me*) in the paper. The correct values of the decreased energy of the bandgap narrowing (ΔEBGN) and the increased energy of the Burstein-Moss effect (Efn) are 120 meV and 140 meV instead of 140 meV and 160 meV, respectively. Consequently, for the heavily Si-doped GaAsN, the correct value of me* is 0.11m0 instead of 0.098m0, where m0 is the electron mass. Figure 2 with the correct value is presented below. 1 Figure (Figure presented.) PL spectra of heavily Si-doped GaAsN with [Si] of 2 × 1019 cm−3 and [N] of 0.6% as a function of temperature. Black arrows indicate PL peak energy on each PL spectrum. 2 Figure (Figure presented.) Temperature dependence of PL peak energy for heavily Si-doped GaAsN with [Si] of 2 × 1019 cm−3 and [N] of 0.6% and moderately Si-doped GaAsN with [Si] of 1 × 1018 cm−3 and [N] of 0.7%. The authors state that these errors do not change the scientific conclusions of the paper in any way and apologize for any confusion this may have caused.

    DOI

    Scopus

    1
    被引用数
    (Scopus)
  • Photoluminescence Mechanism in Heavily Si-Doped GaAsN

    Takashi Tsukasaki, Ren Hiyoshi, Miki Fujita, Toshiki Makimoto

    Crystal Research and Technology   56 ( 3 )  2021年03月  [査読有り]

    担当区分:筆頭著者, 責任著者

     概要を見る

    The photoluminescence (PL) mechanism is discussed for heavily Si-doped GaAsN, and the evaluation method of electron effective mass (me*) is proposed using its PL peak energy. PL peak energy monotonically decreases as increasing temperature, so the S-shape characteristic is vanished for this heavily Si-doped GaAsN as opposed to moderately Si-doped GaAsN. This result shows that the dominant PL process is an optical transition from the Fermi energy to the top of valence band independent of temperature for this heavily Si-doped GaAsN, as with degenerate n-type GaAs. Because PL peak energy is expressed by the sum of bandgap energy, the increased energy of the Burstein–Moss effect, and the decreased energy of the bandgap narrowing, me* is calculated to be 0.098 m0 for this heavily Si-doped GaAsN with nitrogen composition of 0.6%, where m0 is the electron mass. This result agrees well with previous studies, meaning that the method for estimation of me is effective for dilute GaAsN.

    DOI

    Scopus

    1
    被引用数
    (Scopus)
  • Si doping mechanism in Si doped GaAsN

    T. Tsukasaki, R. Hiyoshi, M. Fujita, T. Makimoto

    Journal of Crystal Growth   514   45 - 48  2019年05月  [査読有り]

    担当区分:筆頭著者, 責任著者

     概要を見る

    The Si doping mechanism is systematically investigated in dilute nitride GaAsN grown by radio frequency plasma assisted molecular beam epitaxy (RF-MBE). We change growth temperature, Si impurity concentration ([Si]), and nitrogen composition ([N]). The relationship between Si activation ratio (α) and [N] are evaluated using X-ray diffraction (XRD) 2θ-ω and Hall effect measurement. As [N] in GaAsN increases, α drastically decreases, which is ascribed to mechanisms of inactive Si donors such as a cluster of Si and N at an As site ((Si-N) As ). We find that the main factor of inactive Si donors in GaAsN depends on both [Si] and [N].

    DOI

講演・口頭発表等

  • Suppression of Nitrogen Composition Fluctuation by Beryllium Doping in GaAsN Ternary Alloys

    T. Tsukasaki, T. Tsunoda, K. Inoue, M. Fujita, T. Makimoto

    65th Electric Materials Conference  

    発表年月: 2023年06月

  • Slow photoluminescence lifetime of heavily Be-doped GaAsN

    T. Tsukasaki, H. Sumikura, T. Fujimoto, M. Fujita, T. Makimoto

    36th North American Molecular Beam Epitaxy Conference  

    発表年月: 2022年09月

  • Photoluminescence Mechanism in Heavily Si doped GaAsN, 8th International Symposium on Growth of Ⅲ-Nitrides

    T. Tsukasaki, R.Hiyoshi, M. Fujita, T. Makimoto

    8th International Symposium on Growth of Ⅲ-Nitrides  

    発表年月: 2020年03月

  • Si doping mechanism in Si doped GaAsN

    T. Tsukasaki, R.Hiyoshi, M. Fujita, T. Makimoto

    20th International Conference on Molecular Beam Epitaxy  

    発表年月: 2018年09月

共同研究・競争的資金等の研究課題

  • Alの添加によるGaAsN系混晶の高品質化に関する研究

    パワーアカデミー  パワーアカデミー研究助成

    研究期間:

    2023年02月
    -
    2024年03月
     

  • GaAsNにおける窒素組成の揺らぎに関する研究

    三菱マテリアル株式会社  三菱マテリアル株式会社―早稲田大学理工学術院包括協定にともなう2021年度研究助成

    研究期間:

    2021年04月
    -
    2022年03月
     

  • 高濃度BeドープGaAsNにおけるBe-Nの形成に関する研究

    三菱マテリアル株式会社  三菱マテリアル株式会社―早稲田大学理工学術院包括協定にともなう2020年度研究助成

    研究期間:

    2020年04月
    -
    2021年03月
     

  • BeドープGaAsNにおけるBe原子の活性化機構に関する研究

    三菱マテリアル株式会社  三菱マテリアル株式会社―早稲田大学理工学術院包括協定にともなう2019年度研究助成

    研究期間:

    2019年04月
    -
    2020年03月
     

 

特定課題制度(学内資金)

  • RF-MBE法を用いて低温成長したSiドープGaAsNの電気的特性に関する研究

    2022年   牧本 俊樹

     概要を見る

    分子線エピタキシー法を用いて低温で成長した高濃度Siドープn型GaAsNについて,成長後のアニール温度を変化させて,電子濃度および電子移動度の温度特性における窒素組成依存性を評価した。窒素組成の減少にともなって,GaAsNに固有である局在準位の状態密度が減少するために,SiドープGaAsNにおける電子の活性化エネルギーが相対的に増加した。また,電子移動度の温度特性より,窒素組成によらず,室温付近においてイオン化不純物散乱が支配的であった。これらの実験結果から,非常に低い窒素組成を含む低温成長SiドープGaAsNを高温でアニールすることによって,抵抗率の温度変化率が極大化することを明らかにした。