Thermal degradation comparison of delta-doped GaAs tunnel junctions using Si and Te n-type dopants

Tunnel junctions (TJs) are essential for high-performance multijunction solar cells to act as transparent low resistance paths carriers travel between adjacent cells. However, TJs typically exhibit highly degraded tunneling performance due unwanted dopant out-diffusion during top cell growth. In this study, GaAs with Si and Te delta-doping (δ-doping) were grown via solid source molecular beam epitaxy investigate the thermal stability. While δ-doped exhibited typical characteristics an Esaki peak current density of 173 A/cm2, revealed 1.5 A/cm2 at Vbias = 100 mV without negative resistance. It was found that degradation after annealing 600 °C 90 min significantly higher δ-doping than Te. Secondary ion mass spectroscopy measurements reveal shows no clear signs diffusion while significant in active TJ layer annealing. The superior stability compared proves be advantageous alternative n-type high temperature long duration multi-junction