Optimization of p-doping in AlGaAs grown by CBE using TMA for AlGaAs/GaAs tunnel junctions

•Controlled p-doping of AlGaAs grown by CBE using TMA by varying growth parameters.•Tunnel junctions showing peak tunneling current as high as 6136 A/cm2.•Low temperature growth was found to be ideal for tunnel junction performances.•C incorporation mechanisms differ in temperature from TMGa.

Trimethyl aluminium (TMA) was used as an intrinsic dopant source to grow highly p-doped AlGaAs by chemical beam epitaxy (CBE). Growth parameters were varied to control doping level, and three sets of growth parameters were identified to maximize the hole concentration in CBE-grown AlGaAs: low temperature growth; low V/III ratio combined with high growth rate; aluminium-rich composition. AlGaAs/GaAs tunnel junctions were fabricated using each of these set of growth parameters and tunneling peak currents as high as 6136 A/cm2 were obtained. These tunnel junctions are suitable for use in very high concentration multijunction solar cells.