NOVELTY - A solar cell module comprises a primary solar cell including a primary semiconductor region including a primary conductivity-type primary terminal and a secondary conductivity-type secondary terminal, and a secondary semiconductor region, and a secondary solar cell. The primary semiconductor region of primary solar cell comprises a primary subcell including a germanium substrate with diffusion region doped with n-type dopant including phosphorus and arsenic, and a secondary subcell including a layer of gallium arsenide disposed over substrate, and a nucleation layer.    USE - Solar cell module is used in satellite application and space application.    ADVANTAGE - The solar cell in the module efficiently converts energy.    DETAILED DESCRIPTION - A solar cell module comprises a primary solar cell including a primary semiconductor region including a primary conductivity-type primary terminal on an upper surface of the primary solar cell and a secondary conductivity-type secondary terminal on the lower surface of the primary solar cell, and a secondary semiconductor region, and a secondary solar cell disposed adjacent to the primary solar cell. The primary semiconductor region of primary solar cell comprises a primary subcell including a germanium substrate with diffusion region doped with n-type dopant including phosphorus and arsenic, and a secondary subcell including a layer of gallium arsenide or indium gallium arsenide disposed over substrate, and a nucleation layer in direct physical contact with the substrate. The secondary semiconductor region of primary solar cell includes a primary bypass diode having a primary conductivity-type primary terminal and a secondary conductivity-type secondary terminal. The secondary conductivity-type terminal is electrically-isolated by the semiconductor regions of the primary solar cell. The secondary solar cell includes a primary semiconductor region including a primary conductivity-type primary terminal on upper surface of the secondary solar cell and secondary conductivity-type secondary terminal on the bottom surface of the secondary solar cell, and secondary semiconductor region. The primary semiconductor region of the secondary solar cell comprises a primary subcell including a germanium substrate with diffusion region doped with n-type dopant including phosphorus and arsenic, a secondary subcell comprising layer of gallium arsenide or indium gallium arsenide disposed over substrate, and nucleation layer in direct physical contact with the substrate. The nucleation layer controls diffusion of arsenic atoms in the substrate. The nucleation layer is free of arsenic. Upper portion of diffusion region has high concentration of phosphorus atoms than arsenic atoms. Lower portion of diffusion region has high concentration of arsenic atom then phosphorus atoms. The secondary semiconductor region of the secondary solar cell includes a secondary bypass diode having a primary conductivity-type primary terminal and a secondary conductivity-type secondary terminal. The secondary conductivity-type terminal is electrically-isolated by the semiconductor regions of the secondary solar cell. The secondary conductivity-type secondary terminal of primary bypass diode of primary solar cell is electrically-connected to primary conductivity-type primary terminal of the secondary solar cell. The primary conductivity-type primary terminal of primary bypass diode of the primary solar cell is electrically-connected to the secondary conductivity-type secondary terminal of the primary solar cell and to the primary conductivity-type primary terminal of the secondary solar cell.    DESCRIPTION OF DRAWING(S) - The drawing shows a schematic view of the solar cell module.    Solar cell semiconductor structures (400,500,600,700)    Integral bypass diode (470,570,670)    External electrical interconnect (490)    Multi-junction solar cell structures (501,601,701)    Tandem solar subcells (504,506,508,604,606,608,704,706)