NOVELTY - The tunnel junction (290) comprises p-doped and n-doped tunnel layers having indium phosphide lattice constant. The p-doped tunnel layer is p-doped material of aluminum gallium indium arsenide (AlGaInAs) and n-doped tunnel layer is n-doped material selected from group consisting of indium phosphide (InP), indium gallium arsenide phosphide (GaInPAs), aluminum arsenide antimonide (AlAsSb), aluminum indium arsenide antimonide (AlInAsSb) and aluminum indium phosphorus arsenide (AlInPAs).    USE - High band gap type II tunnel junction of photonic device (claimed) such as multi-junction solar cell e.g. indium phosphide based dual junction solar cell used in space applications. Can also be used in other photonic devices such as laser power converter or sensors for converting light to electricity.    ADVANTAGE - The efficiency and performance of solar cell are improved. The tunnel junction having increased tunneling current is provided, while increasing tunneling probability and peak tunneling current of tunnel-diode for handling higher solar intensity with narrower space charge region. The material growth process is improved. The optical transparency is improved, thus reduced optical parasitic loss. The complexity of cell structure design and corresponding metal organic vapour phase epitaxy (MOVPE), growth are reduced by providing single band gap binary semiconductor layer.    DETAILED DESCRIPTION - The p-doped tunnel layer is a p-doped material selected from group consisting of aluminum gallium indium arsenide (AlxGa1xInAs), where x is greater than or equal to 0.25 and up to and including x is equal to one. The tunnel layers are grown sequentially in a reactor selected from group consisting of metal organic vapor phase epitaxial reactor, hydride vapor phase epitaxial reactor, molecular beam epitaxy reactor, chemical beam epitaxy reactor and atomic layer deposition reactor.    DESCRIPTION OF DRAWING(S) - The drawing shows a schematic view of the solar cell.    Solar cell (200)    Photovoltaic cell (202)    Window layer (210)    Base (220)    Tunnel junction (290)