A stack-like III-V semiconductor product comprising a substrate and a sacrificial layer region arranged on an upper side of the substrate and a semiconductor layer arranged on an upper side of the sacrificial layer region. The substrate, the sacrificial layer region and the semiconductor layer region each comprise at least one chemical element from the main groups III and a chemical element from the main group V. The sacrificial layer region differs from the substrate and from the semiconductor layer in at least one element. An etching rate of the sacrificial layer region differs from an etching rate of the substrate and from an etching rate of the semiconductor layer region at least by a factor of ten. The sacrificial layer region is adapted in respect of its lattice to the substrate and to the semiconductor layer region.

A stack-like III-V semiconductor product comprising a substrate and a sacrificial layer region arranged on an upper side of the substrate and a semiconductor layer arranged on an upper side of the sacrificial layer region. The substrate, the sacrificial layer region and the semiconductor layer region each comprise at least one chemical element from the main groups III and a chemical element from the main group V. The sacrificial layer region differs from the substrate and from the semiconductor layer in at least one element. An etching rate of the sacrificial layer region differs from an etching rate of the substrate and from an etching rate of the semiconductor layer region at least by a factor of ten. The sacrificial layer region is adapted in respect of its lattice to the substrate and to the semiconductor layer region.

Semiconductor structures including optically-transparent metamorphic buffer regions, devices employing such structures, and methods of fabrication. The optically-transparent metamorphic buffer is grown to provide a lattice constant transition between a smaller lattice constant and a larger lattice constant (or vice-versa), allowing materials with two different lattice constants to be monolithically integrated. Such buffer layer may include at least two elements from group V of the periodic table. The optically-transparent metamorphic buffer region may include digital-alloy superlattice structure (s) to confine material defects to the metamorphic buffer layer, and improve electrical properties of the metamorphic buffer layer, thereby improving the electronic properties of electronic devices such as optoelectronic devices and photovoltaic cells. Photonic devices such as solar cells and optical detectors containing such semiconductor structures.

Semiconductor structures including optically-transparent metamorphic buffer regions, devices employing such structures, and methods of fabrication. The optically-transparent metamorphic buffer is grown to provide a lattice constant transition between a smaller lattice constant and a larger lattice constant (or vice-versa), allowing materials with two different lattice constants to be monolithically integrated. Such buffer layer may include at least two elements from group V of the periodic table. The optically-transparent metamorphic buffer region may include digital-alloy superlattice structure (s) to confine material defects to the metamorphic buffer layer, and improve electrical properties of the metamorphic buffer layer, thereby improving the electronic properties of electronic devices such as optoelectronic devices and photovoltaic cells. Photonic devices such as solar cells and optical detectors containing such semiconductor structures.

According to one embodiment, a multi-junction solar cell includes a first solar cell, a second solar cell, and an insulating layer. The first solar cell includes a first photoelectric conversion element. The second solar cell is connected in parallel with the first solar cell. The second solar cell includes multiple second photoelectric conversion elements connected in series. The insulating layer is provided between the first solar cell and the second solar cell. The second photoelectric conversion element includes a p-electrode and an n-electrode. The p-electrode is connected to a p.sup.+-region including a surface on a side opposite to a light incident surface. The n-electrode is connected to an n.sup.+-region including the surface on the side opposite to the light incident surface. The p-electrodes oppose each other or the n-electrodes oppose each other in a region where the multiple second photoelectric conversion elements are adjacent to each other.

Distributed Bragg reflectors are incorporated into the compositionally graded buffers of metamorphic solar cells, adding functionality to the buffer without adding cost. The reflection aids in collection in subcells that are optically thin due to low diffusion length, high bulk recombination, radiation hardness, partially-absorbing quantum structures, or simply for cost savings. Performance enhancements are demonstrated in GaAs subcells with QWs, which is beneficial when GaAs is not the ideal bandgap.

A method is described that includes sputtering multiple layers on a back surface of the photovoltaic structure, the photovoltaic structure being made of at least one group III-V semiconductor material, and evaporating, over the multiple layers, one or more additional layers including a metal layer, the back metal structure being formed by the multiple layers and the additional layers. A photovoltaic device is also described that includes a back metal structure disposed over a back surface of a photovoltaic structure made of a group III-V semiconductor material, the back metal structure including one or more evaporated layers disposed over multiple sputtered layers, the one or more evaporated layers including a metal layer. By allowing evaporation along with sputtering, tool size and costs can be reduced, including minimizing a number of vacuum breaks. Moreover, good yield and reliability, such as reducing dark line defects (DLDs), can also be achieved.

A method is described that includes sputtering multiple layers on a back surface of the photovoltaic structure, the photovoltaic structure being made of at least one group III-V semiconductor material, and evaporating, over the multiple layers, one or more additional layers including a metal layer, the back metal structure being formed by the multiple layers and the additional layers. A photovoltaic device is also described that includes a back metal structure disposed over a back surface of a photovoltaic structure made of a group III-V semiconductor material, the back metal structure including one or more evaporated layers disposed over multiple sputtered layers, the one or more evaporated layers including a metal layer. By allowing evaporation along with sputtering, tool size and costs can be reduced, including minimizing a number of vacuum breaks. Moreover, good yield and reliability, such as reducing dark line defects (DLDs), can also be achieved.

A multi junction solar cell includes one or more upper cells and a thin-film, polycrystalline, low-bandgap bottom cell. A single-junction solar cell includes a polycrystalline semiconductor thin film, wherein a bandgap of the solar cell is greater than 1.2 eV or less than 1.2 eV, and the solar cell is configured to receive light through two surfaces, such that the bottom cell has bifacial operation.

A multijunction solar cell and its method of fabrication, including an upper and a lower solar subcell each having an emitter layer and a base layer forming a photoelectric junction; a near infrared (NIR) wideband reflector layer disposed below the upper subcell and above the lower subcell for reflecting light in the spectral range of 900 to 1050 nm which represents unused and undesired solar energy and thereby reducing the overall solar energy absorptance in the solar cell and providing thermodynamic radiative cooling of the solar cell when deployed in space outside the atmosphere.