Materials and Device Design with ZnO-Based Diluted Magnetic Semiconductors
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Materials and Device Design with ZnO-Based Diluted Magnetic Semiconductors
Kazunori Sato and Hiroshi Katayama-Yoshida Department of Condensed Matter Physics, The Institute of Scientific and Industrial Research (ISIR), Osaka University, 8-1 Mihogaoka, Ibaraki, Osaka 567-0047, Japan.
ABSTRACT
We propose a materials design to fabricate the transparent and half-metallic ferromagnets in V-, Cr-, Mn+hole, Fe-, Co-, and Ni-doped ZnO based upon ab initio electronic structure calculation. Mn-doped ZnO is anti-ferromagnetic spin glass state, however, it becomes half-metallic ferromagnets upon hole doping. The ferromagnetic state becomes more stable by electron doping in Fe-, Co- or Ni-doped ZnO. From the point of practical applications, it is feasible to realize the half-metallic ferromagnets with high Curie temperature, because n-type ZnO is easily available. We propose the design of new functional devices, such as spin-FET, photo-induced ferromagnets, and spin-injection devices using negative electron affinity in the wide band gap semiconductors.
INTRODUCTION
ZnO attracts much attention as an opto-electronic material because of its wide band gap energy of 3.3 eV and large exciton binding energy of 60 meV. Its cheapness, abundance and harmoniousness with our environment are also appealing. We proposed a new valence control method of codoping with doping Ga (or In, Al) donor and N acceptor at the same time for the fabrication of a low-resistive p-type ZnO based upon the ab initio calculation [1]. Our prediction of the materials design for the fabrication of a low resistive p` -type ZnO is confirmed by the recent successful codoping experiment by laser-MBE [2]. Based upon the success in the valence control of p-type ZnO, we propose a materials design to fabricate the transparent and half-metallic ferromagnets with Mn-doped p-type ZnO upon codoping [3]. Upon codoping with the mobile holes and Mn in ZnO, it is shown that the ferromagnetic state becomes more stable than the anti-ferromagnetic ones due to the ferromagnetic double exchange interaction. It is also found that 3d transition metal atoms of V, Cr, Fe, Co and Ni showed the ferromagnetic ordering of their magnetic moments in ZnO without any additional carrier doping treatments. We found that the ferromagnetic state was stabilized by electron doping in the case of Fe-, Co- or Ni-doped ZnO [4]. From the point of practical applications, it is favorable to realize high Curie temperature (TC)ferromagnet, because n-type ZnO is easily available. Appearance of the low-resistive p-type ZnO and the ferromagnetism in these systems suggest possibility for a fabrication of transparent conductive p-type ZnO and a transparent ferromagnet which have great impact on the industrial applications. We will also discuss the design of new devices, such as spin-FET, photo-induced ferromagnet, and F4.6.1
spin-injection devices using negative electron affinity in the wide band gap semiconductors.
CALCULATION DETAIL
In ZnO-based diluted magnetic semiconductors (DMSs), Zn atoms are substitu
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