The development of nanoelectronic devices calls for Ohmic contacts of very small dimensions. The size dependence of both alloyed and nonalloyed contacts to GaAs and InGaAs is investigated. It is found that alloyed contacts to GaAs fail to achieve Ohmic contact for contacts below 3000 A in diameter, while molecular‐beam epitaxy grown heavily doped InGaAs on GaAs nonalloyed Ohmic contacts can be formed with size as small as 1500 A.