REGROWN OHMIC CONTACTS TO THIN GAAS-LAYERS AND 2-DIMENSIONAL ELECTRON-GAS

We report on the first realization of extremely low resistivity regrown ohmic contacts to a variety of GaAs/AlGaAs structures using selective epitaxy. For planar regrown n+-GaAs contacts to n-GaAs we have obtained contact resistivity values ∼1×10-7 Ω cm2, and ∼1×10-8 Ω cm 2 for lateral contacts to a 10-nm-thick buried n+-GaAs layer. The contact resistances were substantially temperature independent from 77 to 300 K. Regrown contacts to a 2DEG structure exhibited a much higher and temperature-dependent contact resisitivity which could be accounted for (according to numerical simulation) by ∼5×1012 cm-2 traps at the AlGaAs/ regrown GaAs interface. Post-growth annealing of the regrown annealing of the regrown interface drastically reduced the value of contact resistivity for 2DEG structures to ∼2×10-8 Ω cm2.