ALGAAS/GAAS DOUBLE-HETEROJUNCTION HIGH ELECTRON-MOBILITY TRANSISTORS GROWN BY LOW-PRESSURE ORGANOMETALLIC VAPOR-PHASE EPITAXY

AlGaAs/GaAs double-heterojunction high electron mobility transistors (DHHEMTs) grown by low-pressure organometallic vapor phase epitaxy are reported in this communication. The magnetic field-dependent Hall effect measurement was used to characterize the sheet carrier density and electron mobility of the two-dimensional electron gas (2-DEG). At 77 K the sheet carrier density and the electron mobility were 1.38×1012 cm-2 and 52 900 cm2 /V s, respectively, in a DHHEMT structure with an undoped Al0.28Ga0.72As spacer layer of 120 Å, while they were 7.12×1011 cm-2 and 65 100 cm 2 /V s, respectively, in a comparable single-heterojunction HEMT structure. DHHEMT's with 0.5-μm-gate length and 75-μm-gate width have been fabricated with dc saturation current of 500 mA/mm and dc transconductance of 250 mS/mm. These results are comparable to those produced with molecular-beam epitaxy.