Non-destructive, whole wafer assessment of optoelectronic epitaxial materials

Abstract

Two optical techniques, high-spatial-resolution scanning photoluminescence spectroscopy (sPL) and scanning reflectance spectroscopy (sRS), have been developed to provide rapid, non-destructive, whole wafer assessment of III-V materials grown by molecular beam epitaxy (MBE) and metal organic chemical vapour deposition (MOCVD). These techniques have been combined in a single measurement system which is used to evaluate epitaxial layer quality, composition (or emission wavelength) and thickness. The combination of low excitation power density and high data density in the sPL intensity maps produced by this measurement system has been shown to be important in revealing those defects that control the performance of minority carrier devices such as p-i-n detectors. High-resolution sPL wavelength maps may also be generated. These can be used to infer spatial variation in ternary composition and quantum well (QW) thickness. High-density thickness maps of non-QW epitaxial layers are produced by this instrument in the sRS mode. Thickness variations of less than 20 nm are clearly distinguishable. Examples from MOCVD and MBE growth experiments demonstrate the utility of sPL wavelength and sRS thickness maps in the optimisation of epitaxial reactor designs.