Electrically active and hydrogen passivated Zn in GaAs/AlGaAs specifically distinguished during secondary ion mass spectrometry depth profiling

Abstract

A precise control over the depth distribution of major, minor and trace elements in a structure is crucial for practical applications of semiconductors. Thus, reliable characterization tools capable of measuring depth distribution of electrically active impurities are essential to advance currently existing growth technologies. Secondary Ion Mass Spectrometry (SIMS) is frequently used to measure depth profiles of impurity atoms; however it provides only total elemental concentration distribution. In contrast techniques capable of measuring dopant profiles typically omit information concerning electrically inactive impurities. In this work, we propose a method for obtaining quantitative profiles of both active and hydrogen-passivated (inactive) zinc in a GaAs/AlGaAs sample using Ultra Low Impact Energy SIMS (ULIE-SIMS). The key to the procedure is the ability of ULIE-SIMS to measure complex As₃Zn and hydrogen signals. The zinc–arsenic signal is a marker of the active Zn profile, whereas the hydrogen signal delivers information about the hydrogen-passivated impurity profile. Annealing of the sample provides further validation of the method as the observed increase of active Zn and decrease of passivated Zn signals is associated with hydrogen escaping from the sample surface. The presented approach can potentially be used in optimization of growth processes and controlling the level of impurity activation in semiconductor materials.