CCD-based thermoreflectance microscopy has emerged as a high resolution, non-contact imaging technique for thermal profiling and performance and reliability analysis of numerous electronic and optoelectronic devices at the micro-scale. This thermography technique, which is based on measuring the relative change in reflectivity of the device surface as a function of change in temperature, provides high-resolution thermal images that are useful for hot spot detection and failure analysis, mapping of temperature distribution, measurement of thermal transient, optical characterization of photonic devices and measurement of thermal conductivity in thin films. In this paper we review the basic physical principle behind thermoreflectance as a thermography tool, discuss the experimental setup, resolutions achieved, signal processing procedures and calibration techniques, and review the current applications of CCD-based thermoreflectance microscopy in various devices.

We demonstrate thermal imaging using a charge-coupled device (CCD) thermoreflectance lock-in technique that achieves a record temperature resolution of 18 mK, 44 dB below the nominal dynamic range of the camera (from 72 to 116 dB) for 10(5) periods of measurement. We show that the quantization limit of the CCD camera does not set the lower bound on the precision of the technique. We present a theoretical description of the measurement technique, accounting for the effects of noise and nonideal analog-to-digital conversion, resulting in analytic expressions for the probability distribution function of the measured signals, and allowing for explicit calculation of resolution and error bars. The theory is tested against parametrically varied measurements and can be applied to other sampled lock-in measurements. We also experimentally demonstrate sub-quantization-limit imaging on a well-characterized model system, joule heating in a silicon resistor. The accuracy of the resistor thermoreflectance measurement is confirmed by comparing the results with those of a standard 3omega measurement.

Using a charge coupled device-based thermoreflectance technique, we achieve a high-resolution ͑ϳ700 nm͒ cross-sectional temperature profile of a semiconductor laser. This two-dimensional profile allows us to identify separate heat sources due to contact heating and nonradiative recombination in the active region. By adapting the technique to pulsed operation and varying the laser's duty cycle, we measure the thermal relaxation time constant. We also quantitatively determine the heat transfer from device-internal heat sources and demonstrate both the large effect of lateral heat spreading and the distinction between a laser's top surface temperature and its active region temperature.

Beads on a vibrating wire are used to simulate the discrete structure of a solid-state material. The novel idea of the experiment is to use very small oscillation amplitudes of the wire to avoid nonlinearities in the interaction. We achieve a good signal-to-noise ratio using a lock-in technique. We find quantitative agreement between theory and experiment for not only a mono-and a diatomic chain, but also for the bare wire. The latter agreement is the crucial aspect that distinguishes our experiment from previous ones. This agreement assures that the fundamental assumption of the theory ͑Hooke's law͒ is satisfied. We show that the properties of phonon dispersion curves are not special, and that the same band structures occur when the wavelength of any wave becomes comparable to the length scale of a discrete periodicity.