6英寸硅基GaN HEMT外延材料的制备

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

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2.9μm无裂纹（扣除边缘2 mm）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 cm^2/（V·s）,方块电阻为279.8Ω/,电荷面密度为1.07×10^（13）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。

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 cm^2/（ V·s）and 1. 07 × 10^（13） cm^（-2）,respectively,resulting in the sheet resistance of 279. 8 Ω/□. 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 measure-ment,which may be caused by the reduction of carrier concentration due to the Schottky barrier contact in the C-V measurement.