The application of photoreflectance (PR) spectroscopy to metal-semicon
ductor field effect transistor and high electron mobility transistor s
tructures is demonstrated. The line shape analysis relies on a new met
hod for calculating PR spectra and electric field profiles of heterost
ructures with weakly inhomogeneous layers. The method allows inhomogen
eous built-in electric field distributions below the surface to be det
ected. It can be used to determine characteristic parameters of device
structures and to detect quantum states confined to potential wells.
Differences between PR spectra from nominally identical or similar str
uctures are attributed to different interface qualities.