Strained N-AlGaAs/InGaAs/N-AlGaAs selectively-doped double-heterojunction FET

High-current driving strained N-Al0.27Ga0.73As /In0.15Ga0.85As/N-Al0.15Ga0.85As selectively-doped double-heterojunction FETs have been fabricated using highly conductive epitaxial layers grown by MBE. The maximum drain current of 600 mA/mm and high transconductance values of 350 - 470 mS/mm at drain currents of 330 - 400 mA/mm were obtained for 0.5 µm gate FETs. The strained double-heterojunction structures showed high sheet electron concentrations well exceeding 3×10¹²/cm²and sheet resistance of 260 - 320 ohm, which is one third that for conventional GaAs/N-AlGaAs single-hetero-junction structures. Because of large band offset at the bottom heterointerface, short channel effects were greatly reduced. Consequently, the decrease of threshold voltage due to the reduction of gate length from 5 µm to 0.5 µm was only 0.2 V and the drain conductance for 0.5 µm-gate FET was less than 10 mS/mm.