Research On The New Mechanism Of AlGaN/GaN Heterojunction 2DEG Based On Plasma Treatment And Its Applications

As one of the principle members of 3th generation semiconductor,GaN has become the focus of research on semiconductor materials and devices in the world due to its superior material characteristics.Plasma treatment technology is a common semiconductor technology.It can etch,passivate and modulate carrier concentration of semiconductor by adjusting different gas ratio and power conditions.In Al GaN/GaN heterojunction HEMT device,the concentration of 2DEG in the channel can be modulated by F plasma treatment technology,which has realized the application of enhancement HEMT device.Developing new applications of devices through plasma processing has become an important research direction.Plasmon is collective oscillation formed by coulomb interaction between carriers,also named as plasma waves.At room temperature,the concentration of 2DEG in Al GaN/GaN heterojunction is 1×1013cm-2,and the oscillation frequency of plasmon is in the terahertz frequency.For a long time,the high loss of plasma wave in Al GaN/GaN heterojunction 2DEG had restricted the coherent excitation of plasmon terahertz radiation.This thesis explored a plasmon terahertz emitter device based on fluorine plasma treatment of Al GaN/GaN two-dimensional electron gas.The main work of this thesis included the design of a large area grating coupled plasmon terahertz emitter device with periodic concentration difference of 2DEG.By SF6 plasma treatment technology,the concentration of 2DEG in the ungated region in the channel was modulated,and a periodic structure of the difference of 2DEG concentration between the gated region and ungated region was constructed.The radiation power and spectrum of the device were tested at the low temperature of 11 K,and the results showed that the radiation power of the terahertz was 20 p W.Meanwhile,the instability of the device resistance value after SF6 plasma treatment was studied.The device was tested under different gas atmosphere.The test showed that the instability of the device came from the sensitivity to organic volatile gas,and the specific sensitivity mechanism needs further experimental research.Based on this discovery,it is expected that GaN material can be used as a wearable and integrated gas sensor.