| Budget Amount *help |
¥14,200,000 (Direct Cost: ¥14,200,000)
Fiscal Year 2006: ¥6,600,000 (Direct Cost: ¥6,600,000)
Fiscal Year 2005: ¥7,600,000 (Direct Cost: ¥7,600,000)
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| Research Abstract |
The objective of this research is to realize p-type Zn(Mg)O quasialloys, which consist with superlattices of p-type wide band gap oxide semiconductors and Zn(Mg)O thin films, and can be coherently grown on Zn(Mg)O. Zn(Mg)O semiconductors, being supported by their unique excitonic properties, have attracted increasing attentions toward their applications to ultraviolet optical devices such as light emitting diodes. However, the difficulty in achieving p-type conductivity has significantly obstructed their applications. This research, based on our original technologies, contributes to offer the breakthroughs to overcome the above problems and to promote the device applications of Zn(Mg)O semiconductors.
As candidate materials with which Zn(Mg)O forms superlattices, we considered cupper-based oxides such as CuO, Cu_2O, CuInO_2, CuGaO_2, and CuAlO_2. These materials exhibit p-type conductivity and their shapes of crystal planes are similar to that of c-axis oriented hexagonal ZnO. Among them, an attention has been focused on CuGaO_2 because of its wide band gap energy of 3.6eV, delafossite crystal structure that can be matched to c-faces of ZnO, and small lattice mismatch, smaller than 1%, to ZnO.
The crystal growth has been done by molecular beam epitaxy (MBE). The irradiation of Cu and O resulted in CuO films. The CuO crystal takes cubic structure but a very thin film on ZnO has grown coherently to ZnO keeping hexagonal structure. However, no p-type conductivity was confirmed with CuO. On the other hand, the irradiation of Ga and O formed Ga_2O_3. This has very wide band gap of close to 5eV and exhibited sharp absorption edges. The alloys of both materials, CuGaO_2, showed p-type conductivity with the carrier concentration of 9×10^<14>cm^<-3> and Hall mobility of 3. 5cm^2/Vs. This result was successfully followed by p-type CuGaO_2/ZnO superlattices with the carrier concentration of the order of 10^<14>cm^<-3>.
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