Quantitative Analysis of Dopant Distribution and Activation Across p-n Junctions in AlGaAs/GaAs Light-Emitting Diodes Using Off-Axis Electron Holography

Off-axis electron holography has been used to measure the electrostatic potential profile across the p-n junction of an AlGaAs/GaAs light-emitting diode with linearly graded triangular AlGaAs barriers. Simulations of the junction profile showed small discrepancies with experiment when the nominal dopant concentrations of Si and Be impurities were used. Revised simulations reproduced the measurements reasonably using reduced dopant levels that reflected the efficiency of dopant activation. Band-edge diagrams simulated with the nominal and revised dopant concentrations were also compared in terms of the effect that activation efficiency had on the AlGaAs barrier shape and carrier transport. It is concluded that electron holography measurements combined with modeling offer device designers and growers a helpful tool for analyzing and confirming doping profiles in complex heterostructures.