Near Field Optical Studies of Semiconductor Heterostructures and Laser Diodes

Neareld optical microscopy and spectroscopy is emerging as a powerful tool for the investigation of semiconductor structures. Tunable excitation combined with subwavelength resolution is providing an unprecedented level of detail on the local optical properties of semiconductor structures. Recent neareld optical studies have addressed issues of laser diode mode pro ling, minority carrier transport, neareld photocurrent response of quantum well structures and laser diodes, imaging of local waveguide properties, and location and studies of dislocations in semiconductor thin lms. We present results on the intrinsic resolution limitations of neareld photoconductivity in quantum well heterostructures and demonstrate that the resolution depends strongly on the amount of evanescent and propagating eld components in the semiconductor. Spectroscopic mode-pro ling of high-power laser diode emission details the spatial dependence of multiple spectral modes. This paper presents an overview of NSOM techniques for semiconductor systems, its limitations, and present status.