(Invited) MBE-Grown GaAs/N–AlGaAs Heterostructures and Their Application to High Electron Mobility Transistors

Abstract

Quasi-two-dimensional electron gas accumulating at the heterojunction interface in selectively doped GaAs/N–AlxGa1-xAs (x=0.3) grown by MBE showed extremely high mobilities of 8720 cm2/V·s at 300 K, 122000 cm2/V·s at 77 K, 260000 cm2/V·s at 5 K and 396000 cm2/V·s at 5 K (under light exposure). The mobility attained at 5 K is the highest for MBE grown semiconductor materials. An enhancement mode high electron mobility transistor (HEMT) with a short gate (LG=2 µm), fabricated from the heterostructure material, exhibited transconductance as high as 193 mS/mm of gate width at 300 K and 409 mS/mm at 77K. Furthermore, a 27-stage ring oscillator using HEMTs with gate lengths of 1.7 µm showed propagation delays of 56.5 ps at 300 K (with 0.46 mW of power dissipation per gate) and 17.1 ps at 77 K (0.96 mW). Performance of these devices at 77 K, which is the best ever reported, indicates that the HEMT has great potential for application to high-speed, low power integrated circuits.