Based On The Injection And Oxidation Process Of The Gan Mos Device

As one of the third generation semiconductor materials, Gallium Nitride (GaN) have been widely used for high frequency, high power electric devices and photoelectric devices for its good physical and chymic characteristics. And there has been great interest in development of GaN based metal-oxide-semiconductor (MOS) transistors because of their lower leakage currents and power consumption and capability for greater voltage swings relative to the common GaN high electron mobility transistor (HEMT) devices. However, there are many problems still badly restrict improving performance of the GaN MOS devices such as high interface state density of the gate dielectrics or low electron mobility of the invension channel. In this work, some important processes such as ion implantation for the source/drain regions high doping and thermal oxidation for the gate dielectric materials are investigated. The major study content is listed.1. The Spectroscopic Ellipsometry (SE) measurements of GaN multilayer structures such as n+AlGaN/n-AlGaN/SL/AlN/Sapphire are investigated. Metrical results indicate the SE measurement is exact and which can be used for the analysis of GaN ion implantation and thermal oxidation samples later.2. GaN ion implantation process and rapid thermal annealing(RTA) process after implantation are investigated, and the implantation defect, electrical and optical characteristics of the samples are studied by High-resolution X-ray diffraction (HRXRD), SE, Hall and photoluminescence (PL). HRXRD analyse indicates that higher dose implantation causes more ion-implanted damage, which can be effectively but not completely recovered by RTA up to 1100°C. Hall metrical results indicate RTA at 1100°C with implantation dose 1016cm-2, the sample presents strong n-type conductivity, reaching a maximum sheet carrier concentration 2×1015cm-2 and a minimum sheet resistance 100Ω/square, which is significant for GaN MOS device fabrication in the future.3. The thermal oxidation process in dry oxygen O2 on GaN for MOSFET gate dielectric materials are investigated, oxidation temperature is 900°C, oxidation time is 15min to 4h. SE measurement indicates the average grown rate is about 25nm/h and the refractive index of gallium oxide is 1.8~2.1 which is agree with the prevenient Ga2O3 study results. XPS measurements indicate the gallium oxide is Ga2O3 and the ratio of Ga to O is about 1.2, which is induced by the existence of much oxygen loss. The oxidation process is stable and controllable, and better cleaning and larger O2 flux are useful to improve the oxidation stability and decrease obviously the carbon contamination through the contrastive oxidation experiments. However, the electric characteristic and the interface states of Ga2O3/GaN structures have not been well analyzed, which is the shortage of this paper and would be studied later.In conclusion, the emphasis of this paper is on the separate process study and characterization of material properties for the GaN MOSFET fabrication. And the real device fabrication will be studied deeper in the future.