Fabrication Of Inverted-structure GaN HEMT And Its Photoelectric Integrated Device

Upon satisfying the application of the next generation high-power and high-efficiency electronic devices and optoelectronic devices,significant progresses have made in the reaserch of the third generational semiconductor materials,which mainly consist of GaN,in the past twenty years.GaN based materials are replacing conventional Si and GaAs materials,especially in the fabrication of AlGaN/GaN high electron mobility transistors(HEMTs)and Light emitting diodes(LEDs).LEDs have been widely commercialized and become the main force of a new generation of green lighting.However,the HEMTs have not been widely used because the high price and the remain problems in device performance and fabrication process.In order to improve the device performance and cost performance,we aim to design new process paths,develop new device structures,and fabricate new integrated devices.By fabricating and studying the inverted-structure GaN HEMT and its photoelectric integrated device,we want to optimize the performance of GaN electronic devices and accelerate the development of GaN materials and devices.Firstly,we introduced a new structured ohmic electrode which was in contact with AlGaN/GaN heterostructure interface.Unlike conventional ohmic electrode annealing at 850℃,the new electrode only needed 600℃ annealing to realize good ohmic contact.Compared to conventional HEMT devices,the devices with the new structured ohmic electrodes had lower sheet resistance(reducing by 24.5%)and higher saturation current(increasing by 23%).Secondly,we designed and fabricated a inverted-stucture HEMT with sandwich-structured gate.After substrate transfer,the inverted AlGaN/GaN heterostucture was wrapped by a bottom gate and top field plate and lay on AlN dielectric materials.Due to the passivation reduced the leakage through Si substrate and the top field plate alleviated the peak electric field,the inverted-structure HEMT had higher breakdown voltage than conventional planar devices(increasing from 535 V to 620 V).Besides,the inverted-structure HEMT had a larger gate voltage swing(increasing 2.7 V to 6 V).Thirdly,we developed a monolithic integration device of a vertical-structure InGaN/GaN LED and an inverted-structure AlGaN/GaN HEMT fabricated by the selective epitaxial removal and substrate transfer.When the interconnection was formed,compensational Mg-doping was used to alleviate etching damage and reduce on-state resistance of the integrated device.The current and light output power of the prepared light module can be controlled by the HEMT.Compared with the previous monolithically integrated devices,the reported lighting modules had much higher light output power per module area(LOPMA)of 12.5,around 4 to 10 times the previous ones.Likewise,integrated devices with the vertical-structure LEDs had much higher equivalent external quantum efficiency(EEQE)of 6.15%,around 5 to 20 times larger than the previous ones.As a result,by optimizing device process,designing device structure,and developing device integration,we have obtained inverted-structure GaN based HEMT devices,the performance of GaN based HEMT and its optoelectronic devices was improved.This reaserch will have a certain guidance and reference significance to the further study on GaN materials and devices.