Saturated photovoltage, built-in potential and bandgap-narrowing in homojunction solar cells

Bandgap narrowing limits the open-circuit voltage of p-n junction solar cells both at low and high-level injection. The authors develop a method to estimate bandgap narrowing (and the accompanying reduction in built-in potential) using capacitance-voltage measurements. They then apply the method to hyperabrupt heavily doped GaAs diodes grown by molecular-beam epitaxy. The measured results clearly indicate substantial bandgap narrowing in heavily doped GaAs.