Nagata Takahiro, Suemoto Yuya, Ueoka Yoshihiro, Mesuda Masami, Sang Liwen, Chikyow Toyohiro
National Institute for Materials Science (NIMS), Research Center for Functional Materials (RCFM), Tsukuba, Ibaraki 305-0044, Japan.
NIMS, International Center for Materials Nanoarchitectonics (WPI-MANA), Tsukuba, Ibaraki 305-0044, Japan.
ACS Omega. 2022 May 31;7(23):19380-19387. doi: 10.1021/acsomega.2c00957. eCollection 2022 Jun 14.
The ability to control the polarity of an all-sputtered epitaxial GaN/AlN/Al film on a Si(111) substrate via intermediate oxidization was investigated. A stable surface of GaN on a Si substrate is a N-terminated surface (-c surface); hence, for electric device applications, the Ga-terminated surface (+c surface) is preferable. The GaN/AlN/Al film on Si(111) showed a -c surface, as confirmed by time-of-flight low-energy atom scattering spectroscopy (TOFLAS) and X-ray photoelectron spectroscopy (XPS). The AlN layer was intentionally oxidized via air exposure during film growth. The GaN surface subjected to the oxidization process had the +c surface. Secondary-ion mass spectrometry measurements indicated a high oxygen concentration after the intentional oxidization. However, the intentional oxidization degraded the crystallinity of the GaN/AlN layer. By changing the oxidization point and repeating the GaN/AlN growth, the crystallinity of GaN was recovered. Such polarity control of GaN on Si grown by sputtering shows strong potential for the fabrication of large-diameter +c-GaN template substrates at low cost.
研究了通过中间氧化来控制在Si(111)衬底上全溅射外延GaN/AlN/Al薄膜极性的能力。Si衬底上GaN的稳定表面是N端表面（-c表面）；因此，对于电子器件应用而言，Ga端表面（+c表面）更可取。如飞行时间低能原子散射光谱（TOFLAS）和X射线光电子能谱（XPS）所证实的，Si(111)上的GaN/AlN/Al薄膜呈现出-c表面。在薄膜生长期间，通过空气暴露有意地氧化AlN层。经过氧化过程的GaN表面具有+c表面。二次离子质谱测量表明在有意氧化后氧浓度很高。然而，有意氧化降低了GaN/AlN层的结晶度。通过改变氧化点并重复GaN/AlN生长，GaN的结晶度得以恢复。通过溅射在Si上生长的GaN的这种极性控制对于低成本制造大直径+c-GaN模板衬底显示出强大的潜力。
