Materials design of valence control and transparent ferromagnet in ZnO and GaN based upon ab initio electronic structure calculations: prediction vs. experiment

摘要

It is well known that the fabrication of the low-resistivity p-tpe wide band-gap (E_g) semiconductors such as ZnO (E_g chemical bounds 3.3 eV) and GaN (E_g chemical bounds 3.4 eV) is difficult, because so-called uni-polarity or mono-polarity occurs due to the compensation in thesewide band-gap semiconductors. Blue and ultraviolet laser application and high power electronics application in ZnO and GaN has been hampered by their high resistivity of p-type semiconductors. The origin of the difficulty to fabricate low-resistivity wide band-gap semiconductors are (i) the compensation and (ii) the deep energy levels of acceptors with increasing E_g (decreasing the dielectric constant), for example, ZnO:N (300 meV) and GaN:Mg (200 meV). if the acceptor energy level is 500 meV (corresponds to about 4000K), we can only activate the carrier density by less than 10~(-4