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.