Abstract
In the thesis, we apply the photoreflectance (PR) and reflectivity (R) technique on the analysis of heterojunction bipolar transistor (HBT) and vertical cavity surface emitting laser (VCSEL) epitaxial wafers. The samples are grown by metalorganic chemical vapor deposition (MOCVD) method, and the material systems are InGaP/GaAs for HBT, and GaAs/AlGaAs for VCSEL wafers. We can divide the contents of this thesis into three parts. First, from the PR spectrum of HBT wafers, electric field in the collector/base can be obtained by Franz-Keldysh oscillations (FKOs) calculation. Comparing the electric field (F) and doping concentration (Nd), we can find a correlation between F and Nd.Second, from the PR spectrum of certain HBT wafers, there is a background signal between 1.3-1.7 eV. Assisted by wet etching and PR technique, we can find out the origin of this background signal is related to the interface compound between arsenide and phosphide layers. Third, we can do the reflectivity measurement after removing the laser pump beam from PR system. With R spectrum, we can determine where the problems are in VCSEL wafers, for example, the error in thickness and composition.Spectroscopic analysis has been a powerful tool in compound semiconductor measurement, because of its nondestructivity, noncontactness, ease of sample preparing, and the richness of signal.