Growth of tellurium doped broadband (Al0.7 Ga0.3) InP/AlGaAs tunnel junction

Tellurium doped (AlxGa1-x)InP (AlGaInP) is an ideal material for the n side of an ultra-broadband tunnel junction for next generation 5J solar cell structures grown by metalorganic vapor phase epitaxy (MOVPE). Indium mole fraction is selected to reduce the lattice-mismatch and strain caused by the larger atomic size of tellurium when the AlGaInP must be highly doped for the electron states degeneracy. Growth pause at an elevated temperature after AlGaInP growth is employed to provide for a sharp turn-off, avoiding unintended compensation by donors in the subsequent p layer. The turn-on of tellurium is improved using pre-doping process during the temperature ramp before the growth. Electrochemical capacitance-voltage (ECV) result shows that uniform doping level of 71018 cm-3 is obtained in the n side of the tunnel junction with sharp edges at the doping interfaces. The tunneling current density of the fabricated tunnel junction is about 15.0A/cm2.