Research On Silicon-based Gold-free Enhancement Gallium Nitride High Electron Mobility Transistor

Gallium nitride materials gradually step into the power device stage with its wide band gap,high breakdown,high electron mobility,and high electron gas density.These excellent material properties make GaN power devices have better energy efficiency than silicon power devices.As the world's energy resources are increasingly reduced and greenhouse gas emissions are reduced,more efficient power conversion devices are gradually becoming a hot research direction.A system device equipped with a gallium nitride power device can not only improve the efficiency of power conversion but also meet the portable requirements demanded by personal mobile terminals and also can miniaturize home appliances to obtain a wider space.In this context,this paper investigates and fabricates GaN power devices.In order to fabricate a GaN device,first,the ohmic contact of the source and drain electrodes of the device was studied.Gold and gold-free ohmic contacts were investigated.The gold-free Ti/Al/W?20/100/30 nm?layer achieves a minimum contact value of 0.65?/mm at 800°C.Plasma etching was studied to compare the influence of ICP and RF power,the proportion of etching gas Cl₂,and the pressure of different chambers on the etching surface roughness,and the relationship between the contact resistance and the etching time was given which make a reference to the ohmic contact barrier layer recess.Next,two deposition methods for the gate dielectric material are described.Since the SiN_X grown by the high-temperature LPCVD after the gate process will damage the ohmic contact,an Al₂O₃ deposition at 300°C.is used as the gate dielectric layer material for the device with Ni/TiN as a gate metal.An enhanced device with a threshold voltage of 1.2 V was realized by the recessed gate process,but the recessed gate process caused excessive damage to the channel electron gas,resulting in the saturation drain current value dropping to about 5.2 mA.Finally,the reliability of devices jointly developed with partners was studied,including low-temperature gate pulse stress and time-dependent dielectic breakdown measurements.The low-temperature gate pulse test reveals the abnormal behavior of the threshold voltage change under the gate stress,which shows that it decreases first and then increases.A corresponding model is proposed and verified.The effect of gate dielectric area and multi-finger on SiN_X characteristics was discussed by the time dependent dielectric breakdown test.