Analytical Techniques for Electrically Active Defect Detection

Abstract

This chapter aims to review analytical techniques for the detection of electrically active defects in semiconductor materials. In all cases, the operation principles, the strengths, and the weaknesses will be outlined and illustrated for state-of-the-art examples. Based on the impact of deep level defects on the main semiconductor parameters (resistivity, carrier lifetime, fixed space charge, etc.,) one can define different analysis methods: from simple resistivity measurements to more spectroscopic-like techniques, relying on capacitance or current transients obtained after applying bias or optical pulses to a diode structure. While in the pioneering days, Hall effect versus temperature was the technique of reference for deep level studies in silicon and germanium, nowadays, deep level transient spectroscopy is the standard, with high sensitivity for small relative concentrations of defects. In some cases, complementary information can be gathered from admittance spectroscopy, revealing also details on shallow levels in the band gap. However, it turns out that in many practical cases, the carrier lifetime and related device characteristics (generation and recombination current) are more sensitive than the spectroscopic techniques. The possibility for applying these techniques to nanometric structures will be discussed, eventually resulting in what can be considered as single-defect spectroscopies.