Current progress in experimental and theoretical investigations of polarize
d electron emission from semiconductor heterostructures as well as in the d
evelopment of photoemitters of highly polarized electrons is reviewed. Spec
ial attention is paid to the problems of the optimal-choice of the photocat
hode structure, kinetics in title band bending region, and emission current
and charge limitations in the case of intense optical pumping. Examples of
the application of highly-polarized electron sources in medium- and high-e
nergy physics and in the investigation of: surface magnetism are discussed.