Ap+‐AlGaAs/n+‐GaInP heterojunction tunnel diode with band gapEg≊1.9 eV was fabricated by Atomic Layer Epitaxy growth mode using carbon and selenium as thep‐ andn‐type dopants, respectively. The doping levels of 1×1020/cm3and 5×1019/cm3were achieved both in thep‐ andn‐side of the diode, respectively. The diode can be used as the interconnection of the high and low band gap cells in the AlGaAs/GaAs cascade solar cell structure. At the forward current of 15 A/cm2, which is the expected current density at 1000 suns operation, there is only ∼17 mV voltage drop across the tunnel junction. This is the first reported tunnel diode fabricated in high band gap material systems, with performances that exceed the best reported GaAs tunnel diode.