The growth of semi‐insulating LPE layers requires that the donors and acceptors be highly self‐compensated and that Cr be used to form deep acceptor levels. The high compensation can be achieved by systematic bakeouts of the Ga melt, between growths, at a critical temperature which depends on the materials used in the growth system. The optimum bakeout temperatures for , , and systems were found to be 775°, 700°, and 675°C, respectively. By this method, we are able to grow undoped layers having carrier densities in the low 1013 cm−3 range. By adding 0.5 m/o Cr to the melt under the same conditions, we have grown semi‐insulating layers with resistivities in the 106 Ω‐cm range.