We report the growth of a p + -n + -GaAs tunnel diode by atmospheric pressure metalorganic vapour phase epitaxy (MOVPE), using carbon (C) and silicon (Si) as p-type and n-type dopants, respectively. The more efficient incorporation of silicon on donor sites and carbon on acceptor sites, results in a tunnel junction with peak current density up to 50 Acm --2 , and peak-to-valley current ratio up to 20 at room temperature. This represents the best result ever reported for a GaAs tunnel diode by MOVPE. The calculated theoretical peak current density agrees substantially with our experimental and reported results.