A PARTNERSHIP between researchers at Xidian University and Nanjing Electronic Devices Institute is claiming to have broken new ground with the GaN HEMT by combining an ultrathin GaN channel with an AIN buffer layer."As a result, the power characteristics, off-state leakage characteristics, voltage endurance characteristic, linearity and high-temperature performance of the device have been greatly improved," enthuses team spokesman Kui Dang from Xidian University.This team from China is not the first to investigate this particular architecture, which benefits from the switch from a conventionally doped high-resistance GaN buffer to an AIN buffer with a far wider bandgap and the highest thermal conductivity of any common Ⅲ-N. However, previous HEMTs with this design employed GaN channels more than 200 nm thick, with reports offering little detail into the device's carrier transport properties, high-temperature performance or breakdown characteristics. The HEMT fabricated by Dang and colleagues features a GaN channel just 120 nm-thick, realised by modulating the growth mode.Growth of this device exploits previous work by the team, which determined that modulation during the MOCVD process alters the film-forming point of a GaN channel grown on an AIN buffer, opening the door to thinner channels. "That is why the results in previous reports all possess a thick GaN channel," explains Dang.
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