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Lohrmann, A.*; Castelletto, S.*; Klein, J. R.*; 大島 武; Bosi, M.*; Negri, M.*; Lau, D. W. M.*; Gibson, B. C.*; Prawer, S.*; McCallum, J. C.*; et al.
Applied Physics Letters, 108(2), p.021107_1 - 021107_4, 2016/01
被引用回数：38 パーセンタイル：82.81(Physics, Applied)Creation and characterisation of single photon emitters near the surface of 4H- and 6H-silicon carbide bulk substrates and 3C-SiC epitaxially grown on silicon substrates were investigated. These single photon emitters can be created and stabilized by thermal annealing in an oxygen atmosphere at temperatures above 550 
C. Hydrofluoric acid (HF) treatment is shown to effectively annihilate the emission from defects and to restore an optically clean surface. However, the emission from the defects can be obtained after re-oxidation above 550 C. By measuring using standard confocal microscopy techniques, the excited state lifetimes for the emitters are found to be in the nanosecond regime in all three polytypes, and the emission dipoles are aligned with the lattice.
Lohrmann, A.*; 岩本 直也*; Bodrog, Z.*; Castelletto, S.*; 大島 武; Karle, T. J.*; Gali, A.*; Prawer, S.*; McCallum, J. C.*; Johnson, B. C.*
Nature Communications (Internet), 6, p.7783_1 - 7783_7, 2015/07
被引用回数：143 パーセンタイル：96.84(Multidisciplinary Sciences)A new single photon source (SPS) was found in hexagonal silicon carbide (SiC), and the luminescence from the SPS could be controlled by the operation of the pn diode. The SPS showed electro-luminescence (EL) with spectra between 700 and 850 nm (zero phonon line: 745 nm) and the EL could be easily observed at even room temperature (RT). Also, the SPS has very high thermal stability and can be observed even after 1800 C annealing. The luminescence from the SPS was also observed by photo-luminescence measurements at RT. From Ab initio calculation, it was proposed that the silicon antisite defects beneath cubic SiC inclusion are a reasonable structure for the SPS although the identification of the SPS has not yet done.
Johnson, B. C.; 大島 武; McCallum, J. C.*
Journal of Applied Physics, 111(3), p.034906_1 - 034906_6, 2012/02
被引用回数：9 パーセンタイル：37.49(Physics, Applied)The kinetics of dopant-enhanced solid phase epitaxy (SPE) in amorphous germanium (a-Ge) and silicon (a-Si) layers which are created by ion implantation are investigated. Implanted Sb atoms as dopants into a-Ge at concentrations up to 1
10
/cm
are considered and compared to As-implanted layers with similar concentration of As atoms. Although an active Sb concentration above the solubility limit is achieved, a significant portion of the implanted atoms are not. P, As, and B atom enhanced SPE rates in Si are also analyzed. The relative velocities of P and As in Si are similar to those of As and Sb in Ge. Theoretical predictions on the basis of a simple form of the generalized Fermi level shifting model well agree with the results experimentally obtained in this study.
Johnson, B. C.; 大島 武; McCallum, J. C.*
no journal, ,
Solid phase epitaxy (SPE) is an efficient process to activate implanted dopants on a low thermal budget. Although SPE is a common processing step in the formation of shallow junctions, a complete model is still lacking. Here, we reassess the dominant SPE model describing the dopant dependence of SPE to include factors related to the strain introduced by high dopant concentrations. A range of parameters cause the SPE regrowth rate to deviate from its intrinsic value, characterized by an activation energy of 2.7 eV for Si and 2.15 eV for Ge, This includes the dopant concentration, pressure and the presence of impurities. It is assumed that the defects are in thermal and electronic equilibrium and that the concentrations of positively or negatively charged defects are determined by the band structure and density of states of the bulk crystal. The SPE regrowth rate is then expected to be proportional to the concentration of these defects. The free parameters of the model are the SPE defect energy level and degeneracy. A comprehensive data set for both Si (As, P and B) and Ge (As, Sb and Al) over a wide range of dopant concentrations and SPE anneal temperatures is used to test this model.
Johnson, B. C.; 大島 武; McCallum, J. C.*
no journal, ,
Solid phase epitaxy (SPE) is an important process used to activate dopants on a low thermal budget in Si and Ge device fabrication. The enhancement of the SPE rate by the presence of dopants is well described by a Fermi level effect as encapsulated by the generalized Fermi level shifting (GFLS) model. Dopant dependent deviations from the model have recently been attributed to dopant-induced lattice strain in the plane of growth. Here, data is presented over a broad range of dopant concentrations and SPE anneal temperatures in both Si and Ge including new results in Sb doped Ge. Although an active Sb concentration above the solubility limit is achieved a significant portion of the implanted atoms are not. Theoretical predictions using a simple form of the generalized Fermi level shifting model which incorporates both dopant and dopant-induced stress effects is shown to agree well with all data. A single set of two parameters are determined which describe the dopant enhanced SPE data well independent of dopant species and concentration.
Johnson, B. C.; 大島 武; McCallum, J. C.*
no journal, ,
イオン注入により表面にpn接合を形成する場合、イオン注入層の固相エピタキシャル成長(SPE)が重要となる。熱処理中、結晶構成原子は、注入によりアモルファス化した領域と結晶化領域の界面(c-a界面)で再配列し、格子が形成される。c-a界面にドーパントを含む場合、ドーパントも格子置換位置に配列し電気的に活性となるが、この際、フェルミレベルの位置により固相エピタキシャル成長速度が増加することが知られている。本研究では、ドーパントのエネルギーレベルと縮退度をパラメータとしてフェルミレベルシフト(GFLS)モデルを用いて、シリコン及びゲルマニウム中のSPE速度を計算した。その結果、これまで実験で得られたシリコン及びゲルマニウムの熱処理によるSPEの実験結果を再現することに成功した。特に、ゲルマニウム中のアンチモンとヒ素では同じドーパント濃度であっても格子歪の効果によりSPE速度が異なることもよく再現する結果を得た。
大島 武; 小野田 忍; 牧野 高紘; 岩本 直也*; Johnson, B. C.*; Lohrmann, A.*; Karle, T.*; McCallum, J. C.*; Castelletto, S.*; 梅田 享英*; et al.
no journal, ,
固体中の単一発光源(SPS)の有するスピンや発光を制御することで、量子コンピューティングやフォトニクスを実現しようという試みが行われている。本研究ではSiCを母材としたSPSの探索を行った。半絶縁性(SI)六方晶(4H)SiC基板に室温にて2MeVのエネルギーの電子線照射後、Ar中、30分間の熱処理を行った。室温又は低温におけるフォトルミネッセンス(PL)測定及び室温における共焦点蛍光顕微鏡(CFM)を用いたアンチバンチング測定によりSPSを探索した。110
/cm
の電子線照射後に300Cで熱処理を行った試料に対して80KでのPL測定を行ったところ、850
950nm付近にSi空孔が起因のVラインと呼ばれるPL発光が、650700nm付近にC
V
起因のABラインと呼ばれる二種類のPL発光が観測された。ABラインの発光を有する欠陥中心に対して、CFMを用いて室温でアンチバンチグ測定を行った結果、CVが単一発光源であることが判明した。また、これまでSteedsらによりABラインは中性のCVと主張されていたが、ab initio計算から、この波長領域にPL発光を持つためには正に帯電しているCVであるという結果を得た。
大島 武; Lohrmann, A.*; Johnson, B. C.*; Castelletto, S.*; 小野田 忍; 牧野 高紘; 武山 昭憲; Klein, J. R.*; Bosi, M.*; Negri, M.*; et al.
no journal, ,
量子スピントロニクスや量子フォトニクスへの応用が期待される炭化ケイ素半導体(SiC)中の単一光子源(SPS)に関して、デバイス作製の際に用いる高温熱処理といったプロセス後にも安定に存在するSPSの探索を行った。共焦点蛍光顕微鏡(CFM)観察の結果、1600C以上での熱処理後も550600nmの波長帯に室温においても高輝度で発光特性を示すSPSが存在することが確認された。加えて、未熱処理のSiC基板のCFM観察を行ったところ、非常に少量ではあるが同様なSPSが存在することも判明したが、発光は不安定であり、数秒間の観察中に発光が消失してしまうことが見いだされた。そこで、熱処理温度(酸素中、5分間)とSPSの発光の安定性の関係を調べたところ、550C以上の熱処理で発光が安定化することが明らかとなった。
Lohrmann, A.*; Castelletto, S.*; Klein, J. R.*; Bosi, M.*; Negri, M.*; Lau, D. W. M.*; Gibson, B. C.*; Prawer, S.*; McCallum, J. C.*; 大島 武; et al.
no journal, ,
The single photon sources (SPSs) in the visible spectral region were fabricated near the surface of semi-insulating (SI) 4H-silicon carbide (SiC), SI 6H-SiC substrates and 3C-SiC epitaxial films by annealing in dry oxygen. The photoluminescence (PL) with high intensity was observed from samples after oxygen annealing above 550 C although blinking characteristics of PL were observed from samples annealed below 550 C. Also, the samples annealed above 550 C showed blinking characteristics after removing oxygen atoms terminating the surface by HF-etching. Therefore, we can conclude that the oxygen termination is important to obtain stable PL characteristics from the SPSs near the surface of SiC.
