High performance In0.47Ga0.53As tunnel junctions grown by chemical beam epitaxy on InP and GaAs and Si substrates

High performance In_0.47Ga_0.53As tunnel junctions were successfully realized using chemical beam epitaxy on InP, GaAs and GaAs/Si substrates. The achievement of high performance tunnel junctions, besides extremely high hole and electron concentrations requires low interdiffusion of dopant species in the narrow space-charge region of the junction during the device growth procedure. Therefore a relatively low temperature growth process and a good control of interface properties is required. Using chemical beam epitaxy (CBE) high quality InP and InGaAs can be grown at temperatures substantially lower than those used in more conventional liquid phase epitaxy and metalorganic vapor phase epitaxy techniques rendering CBE specially attractive for such tunnel junction fabrication. The peak currents obtained on samples grown on InP substrates are the highest ever reported for such tunnel junctions. These results demonstrate that CBE is perfectly suited for fabrication of InP/InGaAs tandem solar cells