Processing-induced strains at solder interfaces in extended semiconductor structures

The processing-induced strain in unmetallized areas within solder interfaces of packaged, diode laser chips is investigated by spectroscopic methods, namely, degree of polarization of photoluminescence and photocurrent spectroscopy. An unexpected strain component in the unmetallized regions is identified. Based on spectroscopic results used in concert with modeling that employs the finite element method and theoretical results, this strain component is shown to be primarily compressive along the growth direction of the heterostructure used in the laser architecture. This strain component most likely arises due to localized bending of the heterostructure in the unmetallized regions. This example shows how optical spectroscopy can help in analyzing even strains of complex and unknown symmetry.