We demonstrate the selective area growth of GaN on SiO2-masked AlN/Si(111) and GaN/AlN/Si(111) wafers by chemical beam epitaxy (CBE) using triethyl gallium and ammonia. We investigated the selective nucleation process on Si wafers with oxide and nitride masks. The selectivity of the nucleation process was monitored in real time using time-of-flight mass spectroscopy of recoiled ions (TOF-MSRI). Our results show that TOF-MSRI peaks from mask-corresponding elements (Si and O or N) remain unchanged during GaN regrowth on continuous SiO2 layers or nitridated Si(111) within the condition range we explored. The selective growth was confirmed by ex situ scanning electron microscopy analysis. We also found that, depending on the growth conditions, CBE can be used for selective growth of both microcolumnar and planar GaN films. Room temperature photoluminescence studies revealed that both types of films are optically active, which could potentially lead to novel device concepts and applications. © 2000 American Vacuum Society.