We present two types of lateral photodetector devices on Si/Si0.7Ge0.3. These lateral structures are realized by focused laser beam (FLB) induced local B-doping of an n-type modulation doped heterostructure. The introduced dopants form a potential modulation in the plane of the two-dimensional electron gas. The resulting barriers can be used to constrict an electron channel and define a photoconductor on the micrometer scale. Since the FLB process does not introduce damage in the channel, the written lines work also as active region in lateral n-p-n phototransistor structures. Responsivities up to 10(5) A W-1 are achieved with a spatial resolutions of a few micrometers.