Integration of electrochemical capacitance–voltage characteristics: a new procedure for obtaining free charge carrier depth distribution profiles with high resolution

Abstract

A novel electrochemical profiling technique consisting in integration capacitance–voltage characteristics was proposed, developed and proven. The aim is to overcome the insufficient resolution in charge carrier concentration measurements during commonly used electrochemical capacitance–voltage profiling. This is very actual task for modern low-dimensional optoelectronics. According to the introduced “profiling window”, after each etching step the coordinate interval is selected, the concentration distribution in which is to be matched itself and by the first derivative at the edges with the concentration in adjacent intervals. To achieve these conditions the minimum dissipation factor should be maintained for each C–V characteristic at the corresponding etching depth. The method allows both to obtain general free charge carrier concentration depth distribution over unlimited structure depth and to achieve necessary resolution in key regions, even if they are lying at a high depth. Particularly, in GaAs-based heterostructure concentration profile of deep-lying quantum well and a delta layer (ultra-thin (2 nm) profile of dopant with extremely high concentration) were confidently distinguished with magnitude difference of 20% in the dip region in between. Besides, we have shown how quantum-confined objects of different origins give different concentration responses when electrochemical capacitance–voltage profiling with sequential etching. An explanation for this dissimilarity is given.