Two-dimensional profiling of carriers in a buried heterostructure multi-quantum-well laser: Calibrated scanning spreading resistance microscopy and scanning capacitance microscopy

Abstract

We report results of a scanning spreading resistance microscopy (SSRM) and scanning capacitance microscopy (SCM) study of the distribution of charge carriers inside multi-quantum-well (MQW) buried heterostructure (BH) lasers. We demonstrate that individual quantum-well–barrier layers can be resolved using high-resolution SSRM. Calibrated SSRM and SCM measurements were performed on the MQW BH laser structure, by utilizing known InP dopant staircase samples to calibrate the instrumentation. Doping concentrations derived from SSRM and SCM measurements were compared with the nominal values of both p- and n-doped regions in the MQW BH lasers. For n-type materials, the accuracy was bias dependent with SSRM, while for SCM, excellent quantitative agreement between measured and nominal dopant values was obtained. The SSRM was able to measure the dopant concentration in the p-type materials with ∼30% accuracy, but quantitative measurements could not be obtained with the SCM. Our results demonstrate the utility of combining calibrated SSRM and SCM to delineate quantitatively the transverse cross-sectional structure of complex two-dimensional devices such as MQW BH lasers, in which traditional one-dimensional probing using secondary ion mass spectroscopy provides only a partial picture of internal device structure.