AlGaN/GaN HEMT On Si For High Frequency Switching Devices

As the third generation semiconductor material,gallium nitride(GaN)has received broad attention because of its excellent properties such as high breakdown field strength,high electron mobility.At present,the research and application of GaN switching devices have made gratifying progress,but there are still some problems in the development of GaN high frequency chips as the core of their technology,especially in domestic high frequency AlGaN/GaN below 100 V voltage level.The research and application of GaN power devices are basically in a black state.Therefore,the research work of this thesis is based on the high-frequency AlGaN/GaN HEMT chip.Starting from the chip design and process,through the reasonable device structure,many problems in the process of high-frequency AlGaN/GaN HEMT are solved,such as reduce the on-resistance and parasitic parameters of the device,increase the switching speed and operating frequency of the chip,and meet the requirements of high breakdown voltage and high current.The main contents of this paper are as follows:1.The performance of AlGaN/GaN metal-insulator-semiconductor high electron mobility transistor(MIS-HEMT)was investigated.The device uses different gate width,gate length,gate-to-source distance,gate-to-drain distance,and compares and analyzes its DC characteristics and frequency characteristics.Take the case of 0.75 ?m gate length,1 ?m gate-to-source distance,3 ?m gate-to-drain distance and without field plate structure,it exhibits a Vth of-4.2 V,a low ohmic contact resistance of 0.3 ?·mm,a large maximum current density of 991 mA/mm3 a large maximum transconductance of 176 mS/mm,a high breakdown voltage of 355 V,a low off-state leakage current of 4×10-12 A/mm,When the gate voltage is applied with 7 V,the gate leakage current is only 3.6×10-8A/mm,when the drain voltage is 100 V under the off-state,the dynamic on-resistance of the device is only 1.38 times of the static on-resistance.A large cut-off frequency of 17 GHz and a large maximum oscillation frequency of 21 GHz.2.Preparation and study of enhanced P-GaN/AlGaN/GaN HEMT high frequency switching devices.Starting from the device structure design,different gate length and gate width were used to fabricate dual-gate small and multi-finger gate devices.The DC characteristics and frequency characteristics were tested and analyzed.The fabricated devices have the advantages of low contact resistance,stable threshold voltage,and small gate leakage current,a low ohmic contact resistance of 0.5 ?·mm;a large maximum current density of 350 mA/mm;a large maximum transconductance of 65 mS/mm;a high breakdown voltage of 355 V;a low off-state leakage current of 10-7 mA/mm;When the gate voltage is applied with 6 V,the gate leakage current is only 8×10-7 mA/mm;A device with a gate length of 0.75 ?m has a threshold of 0.6 V,and a device with a gate length of 2 ?m has a threshold voltage of 2 V.3.Development of a new nano-channel array device.In the new structure,a nano-channel array device was realized by a method of treating P_GaN with H plasma.Since H reacts with Mg in P_GaN to form a complex,which serves to passivate P-GaN,H treated P-GaN becomes high-resistance GaN(HR-GaN),two-dimensional electron gas(2DEG)is regenerated in the heterojunction under HR-GaN,and P-GaN exhausts the 2DEG in the heterojunction.This new device structure can improve the electric field distribution and increase the breakdown voltage of the device.At the same time,we also use the method of etching AlGaN/GaN to realize nano-channel devices,which has a significant effect in improving the breakdown voltage.