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采用直接描绘电子束刻蚀法制造了用于低噪声极高频(EHF)放大器的亚半微米栅长的高电子迁移率晶体管。调制掺杂的外延结构是用分子束外延法生长的,在10~(12)电子/cm~2的电子浓度时,室温下的霍耳迁移率为8000cm~2/V·sec,液氮温度下为77,600cm~2/V·sec。通过腐蚀通n~+GaAs接触层的凹楷的方法确定了窄达0.28μm的栅长。0.4μm栅长的耗尽型器件的直流跨导超过260mS/mm。对0.37μm栅长的器件,进行了噪声系数和相关增益的测量,在34GHz下,得到了2.7dB的噪声系数和5.9dB的相关增益。还制造了具有240mS/mm跨导的增强型器件,对0.35μm的栅长,在18GHz下,它们的噪声系数为1.5dB,相关增益为10.5dB。这些结果可以和已报导过的最好的0.25μm栅长的GaAsMESFET的噪声系数相匹敌。
A high electron mobility transistor with a sub-half micron gate length for low-noise, very high frequency (EHF) amplifiers was fabricated using direct delineation electron beam lithography. The modulation-doped epitaxial structure is grown by molecular beam epitaxy. At electron density of 10-12 electrons / cm2, the Hall mobility at room temperature is 8000cm2 / Vsec and the liquid nitrogen temperature Under the 77,600cm ~ 2 / V · sec. The gate length as narrow as 0.28 μm was determined by etching the pit of the n + GaAs contact layer. The dc transconductance of a 0.4 μm gate-length depletion device exceeded 260 mS / mm. For a 0.37μm gate-length device, noise figure and correlation gain measurements were performed. At 34GHz, a noise figure of 2.7dB and a correlation gain of 5.9dB were obtained. An enhancement device with a transconductance of 240 mS / mm was also fabricated with a noise figure of 1.5 dB and a relative gain of 10.5 dB for a 0.35 μm gate length at 18 GHz. These results can be comparable to the noise figure of the best reported GaAsMESFET with a gate length of 0.25 μm.