Indium gallium arsenide (InGaAs) and gallium-indium arsenide (GaInAs) are used interchangeably. Dual junction cells can be made on Gallium arsenide wafers. One proposed material is indium gallium arsenide, or InGaAs. Gallium arsenide (GaAs) is a compound of the elements gallium and arsenic. Silicon-germanium is beginning to replace gallium arsenide (GaAs) in wireless communications devices. The primary photodetectors for telecommunications are made from Indium gallium arsenide. MJ-cells are compound semiconductors and made of gallium arsenide (GaAs) and other semiconductor materials. Indium phosphide-based cells have the potential to work in tandem with gallium arsenide cells. It is used standalone or together with gallium arsenide phosphide. MMICs were originally fabricated using gallium arsenide (GaAs), a III-V compound semiconductor. Second to silicon, gallium arsenide (GaAs) is the second most popular semiconductor used. This method is also used with semiconductor materials other than silicon, such as gallium arsenide. The AlGaAs layer confines the electrons to a gallium arsenide region. Most tandem-cell structures are based on higher performance semiconductors, notably gallium arsenide (GaAs). Gallium arsenide, another semiconductor, forms upon co-pyrolysis of trimethylgallium and arsine.