Wide-Bandgap Semiconductors: Nanostructures, Defects, and Applications

International audienceNanostructured wide-bandgap semiconductors (NWS), such as III-nitrides, SiC, ZnO, TiO 2 , diamond, AlN, and BN, have attracted intensive research attention owing to prospective applications in solid-state lighting, solar cells, power electronics, sensors, spintronics, and MEMS/NEMS. These nanostructured semiconductors exhibit tremendous advantages in terms of power capability, energy conversion efficiency , optical properties, radiation strength, high temperature , and frequency operation. Although great progress has been achieved in the synthesis of the NWS materials and promising device applications have been demonstrated since the new century, much further research in the crystallinity improvement, electronic structure control, impurities doping , and devices design need to be carried out. The growth dynamics and the defect physics of NWS should be better understood to push forward their potential applications. This special issue is focused on recent research progress in wide-bandgap semiconductors materials including novel growth strategies of NWS materials, the electronic structure tailoring for functionalization, novel devices concepts, devices physics, and applications in various fields. By using first-principles calculations based on the density functional theory, D. Ma et al. investigated the defects in gallium arsenide. A deep donor level of 0.85 eV below the conduction band minimum on the gallium arsenide crystal surface was disclosed, while the lowest donor level of the defect inside the gallium arsenide bulk was 0.83 eV. The calculations also predicted that the formation energies of internal and surface defects were around 2.36 eV and 5.54 eV, respectively. They concluded that the formation of defect within the crystal was easier than that on surface. This work would assist in tailoring the electronic structures of gallium arsenide, thus favouring the development of high-performance electronic devices. Two papers on ZnO are contributed to this issue. One is on thin film ZnO and the other on 1-dimensional ZnO nanorods. L. Meng et al. report 2-dimensional electron-gas (2DEG) properties of a Zn polar ZnMgO/MgO/ZnO structure with low Mg composition layer (= 0.05) grown on a-plane (11-20) sapphire by radical-source laser molecular beam epitaxy. They observed that the insertion of a thin (1 nm) MgO layer between ZnMgO and ZnO layers in the ZnMgO/ZnO 2DEG structures resulted in an increase of the sheet density and affected the electron mobility slightly. The resultant carrier concentration was as high as 1.1 × 10 13 cm −2 and the Hall mobility was as high as 3090 cm 2 /Vs at 10 K and 332 cm 2 /Vs at RT. The authors also calculated the dependence of carrier sheet density of the 2DEG on ZnMg