NOVELTY - A multijunction solar cell, comprises: a first layer of a tunnel diode of a first p/n type semiconductor material; a delta-doped layer having a similar p/n type doping as the first p/n type semiconductor material; a second layer of the tunnel diode of a second complementary p/n type semiconductor material to the first layer of the tunnel diode and the delta-dope layer; and at least two photovoltaic subcells electrically connected by the tunnel diode.    USE - The multijunction solar cell is useful for converting solar energy into electrical energy, and for industrial application.    ADVANTAGE - The multijunction solar cell is highly efficient, and has improved electrical characteristics.    DETAILED DESCRIPTION - A multijunction solar cell, comprises: a first layer of a tunnel diode of a first p/n type semiconductor material; a delta-doped layer having a similar p/n type doping as the first p/n type semiconductor material, the delta-doped layer substantially thinner than the first layer, the delta-doped layer reaching a dopant concentration substantially higher than a dopant concentration of the first layer, and the delta-doped layer deposited on the first layer; a second layer of the tunnel diode of a second complementary p/n type semiconductor material to the first layer of the tunnel diode and the delta-dope layer, the second layer grown epitaxially on the delta-doped layer; and at least two photovoltaic subcells electrically connected by the tunnel diode. An INDEPENDENT CLAIM is a method of manufacturing a delta-doped interconnection tunnel junction, comprising: growing epitaxially a first layer of a tunnel diode, the first layer using a first dopant; interrupting the step of growing epitaxially the first layer of the tunnel diode; depositing a delta-doped layer of a second dopant of a same acceptor/donor type as the first dopant on the first layer of the tunnel diode, the second dopant in the delta-doped layer reaching a dopant concentration substantially greater than a concentration of the first dopant in the first layer of the tunnel diode; and growing epitaxially a second layer of the tunnel diode, the second layer using a third dopant of a complementary acceptor/donor type to the first dopant and the second dopant.    DESCRIPTION OF DRAWING(S) - The drawing shows a schematic view of an interconnecting tunnel junction having a delta-doped layer.    Top cell (102)    Bottom cell (104)    Reversed biased junction (206)    Highly doped p-type layer (304)    Highly doped n-type layer (306)    Interconnecting tunnel junction with delta-doped layer (402)    N-type delta-doped layer (502)