High performance tunnel junction with resistance to thermal annealing

The availability of high band gap (>1.9 eV) tunnel junctions (TJ) with large peak current densities (Jpk) is crucial for the development of multijunction photovoltaic cells that can operate at concentrations above 1000 suns. Existing TJ designs include thick GaAs layers which reduce the overall efficiency due to absorption. We have developed an n-InGaP/GaAs/p-AlGaAs structure with a GaAs layer that is 50 A or thinner that has an as-grown Jpk above 2000 A/cm2 an annealed Jpk above 1000 A/cm2. Due to the memory effect of the Te n-type dopant, modifications to the shut off time of the DETe precursor produced the high Jpk that was observed.