.algan / Gan Hemts Current Collapse Effects Testing And Simulation Study

Recently, AlGaN/GaN HEMT has been used more and more in high frequency and high power fields. But because of the current collapse and some other reasons, the performance of AlGaN/GaN HEMT is large poorer than that forecasted by the theories.Base on test and computer simulation, current collapse of AlGaN/GaN HEMT is researched. It is found in gate pulse test that IDS of the device drops when the frequency of signal increases. At the frequency of 10, 100, 1k and 10kHz, the IDS collapses respectively by 20%, 29%, 46% and 64%. Changing the width of Vpulse_ and Vpulse+ respectively, we found that the traps and surface states trap electronics in about 6ms and release electronics in about 600μs.In gate pulse condition, when Vpulse_ of the signal is higher than the threshold voltage, each increment of -1V will let IDS drops about 20%. But when Vpulse_ of the signal is lower than the threshold voltage, each increment of -1V will just let IDS drops about 8%.In drain pulse condition, IDS will be larger than that in DC condition. Each 10 times increment of signal frequency will let IDS increases about 8%. This is just opposite to what happened in the gate pulse test.Through simulation we found that FP (field plate) can modulate the temperature of electronics in the channel and the surface electric field, consequently decrease current collapse. The FP can decease the electronic temperature by about 60%. At 8V VDS, for a device with 2μm LGD (distance between gate and drain), 1μm Lfp (length of FP ) and 0.04μm tox (thickness of dielectric) will optimize the electronic temperature. When VDS comes to 100V, the optimum Lfp and tox is respectively 1μm and 0.5μm. In addition, we found that there is an approximately linearity relationship between Lfp and LGD: L fp = ? 0.23 + 0.798LGD.In the same device configuration and external condition, the optimum Lfp for surface electric field is approximately the same as that for electronic temperature.