Solid-state tellurium doping of AlInP and its application to photovoltaic devices grown by molecular beam epitaxy

• The doping of solid-state Te is successfully controlled.
• Growth and properties of Te-doped AlInP grown by MBE were studied.
• Te doped AlInP is applied to the solar cell.
• Te doped AlInP as the window layer reduces lateral spreading resistance.

Solid-state tellurium (Te) is used as an n-type dopant of AlInP grown by molecular beam epitaxy (MBE). The carrier concentration proportionally increases with increasing Te beam equivalent pressure (BEP) up to a high doping density of 1×1019 cm−3. The incorporation of Te into AlInP results in a mirror-like surface at a moderate doping density due to its surfactant effect, while the surface roughness increased with a further rising of Te doping concentration. Furthermore, for the same In and Al flux ratio, the increase of the Te flux leads to a decreased In-content, but little effect on the alloy׳s disorder is observed. The highly Te-doped AlInP was used in a GaAs solar cell as a window layer. As compared with the solar cell with the Si-doped AlInP window layer, the device with the Te-doped AlInP window layer exhibits the higher efficiency and an extended increase under concentrated solar illumination, due to the benefits of the higher doping density in the Te-doped epilayer.