分子束外延AlGaN/GaN异质结场效应晶体管材料

用自组装的氨源分子束外延 (NH3-MBE)系统和射频等离子体辅助分子束外延 (PA-MBE)系统在 C面蓝宝石衬底上外延了优质 Ga N以及 Al Ga N/Ga N二维电子气材料。Ga N膜 (1 .2 μm厚 )室温电子迁移率达3 0 0 cm2 /V· s,背景电子浓度低至 2× 1 0 1 7cm- 3。双晶 X射线衍射 (0 0 0 2 )摇摆曲线半高宽为 6arcmin。 Al Ga N/Ga N二维电子气材料最高的室温和 77K二维电子气电子迁移率分别为 73 0 cm2 /V·s和 1 2 0 0 cm2 /V· s,相应的电子面密度分别是 7.6× 1 0 1 2 cm- 2和 7.1× 1 0 1 2 cm- 2 ;用所外延的 Al Ga N/Ga N二维电子气材料制备出了性能良好的 Al Ga N/Ga N HFET(异质结场效应晶体管 ) ,室温跨导为 5 0 m S/mm(栅长 1 μm) ,截止频率达 1 3 GHz(栅长 0 .5μm)。该器件在 3 0 0°C出现明显的并联电导 ,这可能是材料中的深中心在高温被激活所致

AlGaN/GaN Heterostructure Field Effect Transistor Materials Grown by Molecular Beam Epitaxy

High quality GaN and GaN/AlGaN 2DEG epitaxial layers have been grown on C plane sapphire by NH 3 MBE and PA MBE technique. For GaN epilayers, the room temperature electron mobility of 300 cm 2/V·s, the background electron concentration of 2×10 17 cm -3 and the FWFM of X ray (0002) diffraction rocking curve of 6 arcmin were measured. The highest electron mobility obtained for the AlGaN/GaN 2DEG materials is 730 cm 2/V·s at room temperature and 1 200 cm 2/V·s at 77 K with the sheet electron concentrations of 7.6×10 12 cm -2 and 7.1×10 12 cm -2 ,respectively. The heterostructure field effect transistors (HFETs) made from the 2DEG materials have shown a transconductance of 50 mS/mm with 1 μm gate length, and a cutoff frequency of 13 GHz from the device with gate length of 0.5 μm and gate width of 20 μm. The device shows an obvious shunt conductance, which may be caused by the thermal activation of deep traps in the epilayers at elevated temperature.