Growth And Research On AlN/Si Heterostructure Materials Epitaxy

As the typical wide-bandgap semiconductor, AlN has large thermal conductivity, high carrier saturation drift velocity, high critical breakdown field and fine thermal stability, well radiation resistance. And it is also piezoelectrically active. These advantages make AlN an excellent material, which could be utilized in HF power devices, radioresistant devices, UV detector and HF wide-band communication devices. The heteroepitaxy of wurtzite AlN on the diamond structure of Si is theoretically feasible, however, some problems such as lattice mismatch, thermal mismatch and antiphase domain exist in the practice. Research on AIN/Si heterostructure is significant. On the one hand, it promotes the combination of AlN material and silicon technology, and on the other, the quality of GaN films grown on AlN buffered Si substrate depends on the quality of such heterostructures. In this work, several tasks have been finished:1. The LPCVD system was upgraded, MO sources and carrier gas supply system were added. Measures such independent gas entering system and twin reaction chambers were applied to avoid the Al stain. The "U" form connection was also utilized to simplify the fixing and maintenance. Then preliminary experiments were taken to confirm the performance of the new complex CVD system.2. AlN polycrystal films were heteroepitaxial grown on Si(111) substrate by MOCVD method. The growth condition of nucleation and epitaxy was studied by SEM and Raman method, and the optimized condition is revealed:nucleation time is3minutes and V/III ratio is780, while epitaxial growth temperature is1200oC and V/III ratio is87. AlN surface with mixed polarization was also analyzed, then solutions were considered. Finally the bandgap of AlN polycrystal film was measured by CL, which is6.19eV to6.63eV.3.3C-SiC(111)/Si(l11) complex substrates were prepared by LPCVD method. XRD result revealed the optimized growth temperature of1150oC. These complex substrates could be utilized in the epitaxial growth of AlN films. Modified EDS data was analyzed to show the elemental composition of SiC epitaxial layer. XPS data was measured for comparison, and verified the modified EDS method as a semi-quantitative measurement.