We present an improved photoreflectance (PR) spectroscopy technique upon the prior art in providing a rapid acquisition method of the PR spectrum in a simultaneous and multiplexed manner. Rapid PR (RPR) application is the on-line monitoring of strained silicon. Shrinkage in the silicon bandgap is measured and converted to strain, using theoretical models. Experimental RPR results are in good correlation with Raman spectroscopy.

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A computer-controlled densitometer for data acquisition and high speed analysis of photographically recorded optical emission spectra has been developed. The instrument scans and digitizes spectra and stores the data sequentially in computer memory. A high-resolution linear measurement transducer mounted on a Jarrell-Ash densitometer monitors the plate position as the spectrum is scanned. The transducer measurement is accurate to within 0.001% over a range of about 340 mm on a glass photoplate. Computer algorithms for locating and identifying peaks and for calculating the wavelengths of spectral lines from their positions in the spectrum are described. With the use of a calibration curve based on the measured positions of three known spectral lines, the wavelength of any spectral line can be determined to within 0.005 nm, and the transmittance of a peak in the recorded spectrum can be measured to within 1%. The wavelengths and transmittances of all detectable spectral lines in the digitized emission spectrum are determined in less than two minutes.

Advances in the application of non-contact photoreflectance (PR) spectroscopy to the characterisation of epiwafer device materials are presented. The study examines both vertical cavity surface emitting laser (VCSEL) and heterojunction bipolar transistor (HBTs) device structures. Emphasis is placed on the technologically important applications of VCSEL device material characterisation, for which PR offers the only true non-destructive testing capability, as well as upon the measurement of electric fields in device epiwafers for rf application transistors such as HBTs. This paper demonstrates the application of nondestructive and rapid techniques for evaluation and control of compound semiconductor materials for both VCSEL and HBT technology.