6英寸硅基GaN HEMT外延材料的制备

采用金属有机物化学气相沉积(MOCVD)方法,在6英寸(1英寸=2.54 cm)Si(111)衬底上,使用多层不同Al摩尔组分的AlGaN插入层技术,成功生长出厚度为2.9 μm无裂纹(扣除边缘2mm)的GaN外延层,解决了大尺寸外延片的翘曲度问题,并在此基础上生长了全结构的高电子迁移率晶体管(HEMT)外延片.采用X射线双晶衍射对外延材料结构进行了表征.Hall测试结果表明,HEMT外延材料的迁移率为2 080 cm2/(V·s),方块电阻为279.8 Ω/□,电荷面密度为1.07×1013 cm-2.采用喇曼光谱仪对GaN的应力进行了表征,GaN的喇曼E2(h)峰位于567.02 cm-1,表面受到的张应力为0.170 6 GPa,由于GaN外延层受到的张应力很小,说明插入多层AlGaN后应力已经释放.汞探针C-V测试二维电子气浓度较Hall测试结果偏低,可能是在C-V测试时肖特基势垒接触会降低载流子浓度.

Fabrication of 6-inch Silicon-Based GaN HEMT Epitaxial Materials

Based on the metal organic chemical vapor deposition (MOCVD) method, a 2.9 μmthick crack-free GaN epitaxial layer (excluding the region within 2 mm away from the edge) on the 6-inch (1 inch =2.54 cm) Si (111) substrate was successfully grown by inserting multilayer AlGaN layers with different Al mole fraction,solving the warp problem of large-size epitaxial wafer. In addition, the whole epitaxial structure of high electron mobility transistor (HEMT) was also grown, and the structure of the epitaxial material was characterized by double crystal X-ray diffraction. The Hall measurement results show that the electron mobility and the surface charge density of the HEMT structure are 2 080 cm2/(V·s) and 1.07×1013cm-2,respectively, resulting in the sheet resistance of 279.8 Ω/口. The stress of GaN was characterized by Raman spectrometer. The Raman E2(h) peak of GaN is 567.02 cm-1,and the surface tensile stress is 0.170 6 GPa. The very small tensile stress of GaN epitaxial layer indicates that the stress of GaN epilayer is released with the insertion of AlGaN multilayers. The two-dimensional electron gas concentration obtained by Hg-probe C-V measurement is lower than that by the Hall measurement, which may be caused by the reduction of carrier concentration due to the Schottky barrier contact in the C-V measurement.