Scanning Capacitance Microscopy of Dopants in III-V Semiconductors

Scanning Capacitance Microscopy (SCM) was first developed in 1985 as a method for sensing tip-to-sample spacing for surface topography profiling in connection with the RCA VideoDisc. Williams and coworkers were the first to use an SCM for obtaining dC/dV doping profiles in semiconductors, albeit with a rather modest resolution of 200 nm. More recently, it has been developed as a 50-nmresolution tool for microscopic doping analysis of semiconductors by measuring the tip-to-sample rf capacitance in an AFM controlled by other means, e.g. by laser beam deflection of a cantilever tip. In this paper we report on the application of SCM to study the 2D doping profiles of InP-based devices, such as multi-quantum well lasers. It is particularly convenient to prepare cross sections of III-V devices, since the material readily cleaves on [110] planes, as compared to silicon where cross sections must be obtained by painstaking polishing.