• 한국재료학회지
• /
• 제18권8호
• /
• pp.444-449
• /
• 2008

Samples of GaMnAs, GaMnAs codoped with Be, and GaMnAs simultaneously codoped with Be and Mg were grown via low-temperature molecular beam epitaxy (LT-MBE). Be codoping is shown to take the Ga sites into the lattice efficiently and to increase the conductivity of GaMnAs. Additionally, it shifts the semiconducting behavior of GaMnAs to metallic while the Mn concentration in the GaMnAs solid solution is reduced. However, with simultaneous codoping of GaMnAs with Be and Mg, the Mn concentration increases dramatically several times over that in a GaMnAs sample alone. Mg and Be are shown to eject Mn from the Ga sites to form MnAs and MnGa precipitates.

• Journal of Magnetics
• /
• 제10권3호
• /
• pp.103-107
• /
• 2005

Magnetotransport is a prerequisite to realization of electronic operation of spintronic devices and it would be more useful if realized at room temperature. The effects of Be codoping on GaMnAs on magnetotransport were investigated. Mn flux was varied for growth of precipitated GaMnAs layers under a Be flux for degenerate doping via low-temperature molecular beam epitaxy. Magnetotransport as well as ferromagnetism at room temperature were realized in the precipitated GaAs:(Mn,Be) layers. Codoping of Be was shown to promote formation of MnGa clusters, and annealing process further stabilized the cluster phases. The room-temperature magnetic properties of the layers originate from the ferromagnetic clusters of MnGa and MnAs embedded in GaAs. The degenerately doped metallic GaAs matrix allowed the visualization of the magnetotransport through anomalous Hall effect.

• 한국자기학회지
• /
• 제14권6호
• /
• pp.213-218
• /
• 2004

MBE장비를 이용하여 Mn과 Be nux의 변화를 주면서 Be-codoped GaMnAs를 성장시켰다. Mn flux의 범위는 고용체 특성의 GaMnAs에서, 과도한 nux에 의해 이차상이 형성된 상태까지 변화를 주면서 성장시켰다. Be병행 도핑 효과 연구를 위해 두 가지의 Be flux에서 박막을 성장하여 박막의 특성 변화를 관찰하였다. 과도한 Be도핑을 통해 금속성의 전도를 가지는 상태와, 상대적으로 적은 양의 도핑을 통해 캐리어의 수는 증가하였으나 반도체 전도를 보이는 상태이다. 적은 양의 Be이 병행 도핑된 GaMnAs의 경우, 상온에서 강자성 특성을 보였으나, 이차상 형성에 의한 전기 비저항의 증가와 작은 자기저항에 의해 자기 수송특성을 관찰하지 못했다. 그러나 많은 Be도핑에 의해 금속 거동을 보이는 경우에는 많은 수의 캐리어와 전기 전도토의 증가로 인해 자기 수송 특성을 관찰할 수 있었다. Be병행 도핑은 GaAs 기지 내에 효과적으로 캐리어를 공급하고, 이차상 MnAs 뿐만 아니라 MnGa의 형성을 촉진하는 것으로 생각된다.

• 한국자기학회:학술대회 개요집
• /
• 한국자기학회 2004년도 하계학술연구발표회 논문개요집
• /
• pp.26-27
• /
• 2004

• 한국재료학회지
• /
• 제15권1호
• /
• pp.73-77
• /
• 2005

Motivated by the enhanced magnetic properties of Mg-codoped GaMnN ferromagnetic semiconductors, Be-codoped GaMnAs films were grown via molecular beam epitaxy with varying Mn flux at a fixed Be flux. The structural, electrical, and magnetic properties were investigated. GaAs:(Mn,Be) films showed metallic behavior while GaAs:Mn films showed semiconducting behavior as determined by the temperature dependent resistivity measurements. The Hall-effect measurements with varying magnetic field showed clear anomalous Hall effect up to room temperature proving ferromagnetism and magnetotransport in the GaAs:(Mn,Be) films. Planar Hall resistance measurement also confirmed the properties. The dramatic enhancement of the Curie temperature in GaMnAs system was attributed to Be codoping in the GaMnAs films as well as MnAs precipitation.