A linear motion Ga source has been constructed and tested for smooth f
lux variation, The beam flux can be monitored by sensors such as atomi
c absorption, RHEED, and pyrometric interferometry. We demonstrated st
able and reproducible operation of the source using sensor feedback. C
onstant layer composition can be maintained despite Ga thermal desorpt
ion at high temperatures. Arbitrary composition profile can be easily
achieved for band gap engineering.