采用归一化能量1 Me V的中子脉冲反应堆对Al Ga N/Ga N异质结材料进行了辐照研究。实验发现,经1015cm-2注量的中子辐照后,异质结材料的二维电子气(2DEG)载流子浓度(ns)下降,而2DEG迁移率由于受到ns的调制作用略有增加,同时辐照导致的载流子浓度ns下降造成了沟道串联电阻的增加和异质结构阈值电压(VTH)的正向漂移。分析认为,辐照感生类受主缺陷是造成ns下降和阈值电压漂移的原因。原子力显微镜(AFM)和X射线衍射仪(XRD)的测试结果表明,辐照后材料的表面形貌有所恶化,材料应变基本不变,而材料的螺位错和刃位错密度辐照后都略有增加。此外,实验结果还表明初始材料质量越好,辐照退化越小。
Fabrication of enhancement-mode high electron mobility transistors on AlGaN/GaN heterostructures grown on sapphire substrates is reported. These devices with 1.2μm gate-length,4mm space between source and drain,and 15nm recessed-gate depth exhibit a maximum drain current of 332mA/mm at 3V, a maximum transconductance of 221mS/mm, a threshold voltage of 0.57V, ft of 5.2GHz, and fmax of 9.3GHz. A dielectric layer formed unintentionally during recessedgate etching is confirmed by contrasting the Schottky I-V characteristics of pre-etching and post-etching. The frequency characteristics and subthreshold characteristics of the devices are studied in detail.
