Overcoming Difficulties in Photoreflectance Measurements on Product HBTs

摘要

Photoreflectance (PR) is an optical measurement technique used to study material properties and device structures. It is uniquely able to non-destructively measure electric fields within devices. Some device structures such as HBTs have a rough highly doped InGaAs surface layer. In some cases the surface roughness is sufficient to produce light scattering that impedes optical measurements such as PR. We have developed a new measurement configuration separating the pump laser, which causes the light scattering, from the probe laser. Rapid, non-destructive measurements of the emitter and collector depletion regions are possible with this configuration on product wafers with rough surface layers.