AlGaN/GaN HEMT在N2中高温退火研究

通过N2气氛中对蓝宝石衬底AlGaN／GaN HEMT在200～600℃退火1min和5min的多批实验,研究了在不同温度和时间退火冷却后器件直流参数的变化．对器件欧姆接触和肖特基接触在高温退火前后的特性进行了对比分析．确定出了最有利于高电子迁移率晶体管特性提高的退火温度为500℃．退火时间为5min．该条件退火后高电子迁移率晶体管最大跨导提高8．9%．肖特基栅反向漏电流减小2个数量级．阈值电压绝对值减小．退火后肖特基势垒高度提高．在减小栅泄漏电流的同时对沟道电子也有耗尽作用．这是饱和电流和阈值电压变化的主要原因．采用扫描电子显微镜观察肖特基退火后的形貌，500℃未发现明显变化．600℃有起泡现象．

Study of AlGaN/GaN HEMT high temperature anneal in N2

Annealing experiments were carried out at 200~600℃ for 1min and 5min on many batches of AlGaN/GaN HEMTs on the sapphire, and the DC characteristics before annealing and after cooling were compared and analyzed. Also measured were the change of the characteristics of the ohmic contacts and the schottky contacts. It is found that the optimized annealing condition for improving the device characteristics is 500℃ annealing for 5min. Under this condition the maximum transconductance is raised by 8. 9%, the reverse leakage of schottky gate is reduced by two orders of magnitude, and the threshold voltage moves toward the positive direction. The elevation of the schottky barrier height after annealing causes the reduction of gate leakage and the more depletion of channel electrons, which also leads to the change of the saturation current and the threshold voltage. The surface morphology of the schottky contact is observed after annealing by SEM. No obvious change is found for 500℃-annealed samples, but bubbling appears for 600℃-annealed ones.