High transconductance-normally-off GaN MODFETs

Normally-off GaN based modulation doped field-effect transistors have been fabricated. The extrinsic transconductance of MODFETs with gate and channel lengths of 3 and 5 µm, respectively, is as high as 120 mS/mm. The devices exhibit 300 mA/mm current at a positive gate bias of 3 V. This transconductance value compares very favourably with the 45 mS/mm and 24 mS/mm reported earlier for 1 and 0.23 µm gate devices, respectively.