Fabrication Of AlGaN/GaN And Low Temperature Au-free Ohmic Contact Electrode And HEMT Device

AlGaN/GaN heterojunction high electron mobility transistor high electron mobility transistors?HEMTs?has been widely used in high voltage,high frequency,high power semiconductor devices and high performance ultraviolet detectors.In order to reduce the manufacturing costs of AlGaN/GaN HEMTs,the process compatibility between HEMTs and Si-CMOS devices must be realized.It is of great significance to study the low-temperature Au-free ohmic contact technology of GaN-based HEMTs for improving the reliability of HEMT devices and realizing the large-scale manufacture of Si-CMOS process line.In this paper,the AlGaN/GaN Au-free ohmic contact technology is studies.Using Ti/Al/Ti/TiW as Au-free ohmic metal,the structure and process of AlGaN/GaN HEMTs Au-free ohmic electrode have been designed.The effects of the depth of pre-ohmic recess and the annealing condition on the Au-free ohmic contact characteristics of Si-AlGaN/GaN heterojunction were analyzed.The AlGa N/GaN low temperature Au-free ohmic contact electrode has been prepared.The experimental results show that When the pre-ohmic depth is22 nm,the thickness of thin barrier layer and the larger tunneling area greatly improve the electron tunneling,which the electrical properties of the Au-free ohmic contact annealed at600?is obviously better than that of Au-based ohmic contact at high temperature.The resistance and contact resistivity?_c(5.44×10^-5?·cm²)of Au-free ohmic contact are comparable to that of Au-based ohmic contact,while the surface roughness of RMS after annealing is only 3.69 nm.On this basis,AlGaN/GaN MIS-HEMTs devices with Au-free ohmic contacts were fabricated.The test results show that the source-drain saturation current of the device is 468.5 m A/mm@VG+4V and the threshold voltage is-8V.It has good output and transfer characteristics.The breakdown voltage?103V?of samples Au-free at low temperature is higher than that of samples annealed at high temperature?70 V?.Therefore,The AlGaN/GaN MIS-HEMTs device fabriated by Au-free process is helpful to reduce the leakage caused by high temperature annealing and to enhance the breakdown voltage and reliability of the device.