Investigation On Device Characteristics And Reliability Of GaN And In GaN Channel Schottky Barrier Diodes With Recessed Anode

As a kind of ultra-high-speed electronic device with low power consumption,high-voltage and high-temperature resistance,GaN-based SBD plays an important role in the field of power electronics and microwave.Compared with the regular planar anode SBD,the recessed anode SBD can achieve lower turn-on voltage,on-resistance and capacitance,indicating that the recessed SBD has huge advantages in high-frequency and high-power applications.Therefore,it is necessary to carry out extensive and in-depth research on GaN-based SBD.In addition,the In GaN channel heterojunction can effectively improve the mobility of 2DEG,due to In GaN has a narrower band gap than GaN,a deeper electron potential well can be formed when In GaN is used as an insertion channel and grown between the GaN buffer layer and the AlGaN barrier layer.Therefore,InGaN can be used to improve the confinement of 2DEG and increasing the effective surface density of carriers.Based on the above background,this paper mainly studies the electrical characteristics and reliability of the lateral GaN and InGaN channel recessed anode SBD.The main work is as follows:(1)The recessed and regular anode AlGaN/GaN SBD were developed based on silicon substrate.And the electrical properties and the internal mechanism of the two kinds of devices were compared and analyzed.The test results show that the recessed anode Al GaN/GaN SBD has lower turn-on voltage,on resistance and capacitance compared with the regular anode AlGaN/GaN SBD with the same size at room temperature.The I-V characteristics of the device at different temperature show that the thermal stability of the recessed anode device is satisfied.(2)The reliability experiments of high forward current stress were carried out on recessed and regular anode AlGaN/GaN SBD respectively.The degradation rules of the turn-on voltage and on-resistance of the devices were analyzed and the reasons of it were explained.The results show that the degradation of the turn-on voltage and on-resistance of the recessed anode AlGaN/GaN SBD is smaller at the same time.In addition,a 6V voltage stress-recovery experiment was performed on the recessed anode device,and the results show that the turn-on voltage and on-resistance gradually degraded during the stress phase,and gradually recovered after the stress was removed.But they could not be fully recovered,indicating that some of them were permanent degradation.The turn-on voltage degraded faster at the beginning of the stress,which is mainly affected by the traps that already exist in the device,and the turn-on voltage degraded more slowly afterwards,which is caused by the newly generated traps in the stress phase.The degradation mechanism of on-resistance under voltage stress is more complicated.(3)The pulse method MOCVD was used to grow AlGaN/InGaN heterojunction epitaxial material on the sapphire substrate.The results of AFM test showed that the surface of the In GaN channel and the AlGaN/InGaN heterojunction showed clear atomic step morphologies.The RMS roughness values were 0.25 nm and 0.21 nm respectively,indicating that the material has better crystal quality.The HRXRD test was performed on the sample and it can be calculated that the diffraction peak of In GaN is 124.7°,and the composition of In is 5%.The results of variable temperature Hall test showed that the sample has excellent current transport characteristics at high temperatures.(4)Based on the prepared AlGaN/InGaN heterojunction epitaxial material,the recessed anode AlGaN/InGaN SBD has been developed.The device achieves lower turn-on voltage and larger forward current,but the breakdown characteristics are slightly worse.when the anode voltage is 3V.Compared with the GaN channel SBD,the on-resistance,turn-on voltage and reverse current of the In GaN channel SBD have smaller change rates with increasing temperature,indicating that the In GaN channel SBD has more outstanding thermal stability.