The low‐temperature (2 K) photoluminescence (PL) of AlxGa1−xAs (0<x<0.25 was studied in an effort to characterize shallow acceptors in material grown by organometallic vapor phase epitaxy and liquid phase epitaxy techniques. The dominant shallow acceptor in nominally undoped AlxGa1−xAs specimens grown by both techniques was identified as Carbon, withEA=26 meV forx=0.EAwas observed to increase with increasingxto ∼36 meV atx∼0.20, as expected for an effective mass like center whereEA∝[m*(x)/&egr;(x)2]. The PL peak due to the conduction band to acceptor transition was found to become progressively broader with increasingx, which is attributed to increasing donor plus acceptor concentration. The acceptor Ge was studied in intentionally doped LPE specimens. It also behaves as a simple effective masslike center, withEGe∼40 meV for GaAs and 55 meV for Al0.2Ga0.8As, contrary to earlier reports of anomalous behavior.