Low resistance ohmic contacts to two-dimensional electron-gas structures by selective MOVPE

Selective metalorganic vapor-phase epitaxy (MOVPE) has been used to make very-low-resistance edge contacts to thin n+ GaAs layers and to two-dimensional electron gas (2DEG) structures. Contact resistance for contacts to the n+ layer are <1 × 10-8 Ω-cm2, close to its fundamental limit. Computer simulations of the 2DEG structure reveal the influence of traps at the regrown GaAs-AlGaAs interface which deplete the corner region of carriers. This corner region is influenced by the slope of the sidewall. Low-resistance contacts to the 2DEG structures were achieved both through the use of a postgrowth anneal and through the use of vertical sidewalls.