We have studied the capacitance‐voltage (CV) and current‐voltage (IV) characteristics of molecular beam epitaxially (MBE) grownp+‐GaAs/AlAs/n‐GaAs heterostructures as a function of illumination level and temperature. Under illumination we find clear evidence of a hole inversion layer at the AlAs/n‐GaAs interface at 77 K, with a maximum inversion layer carrier concentration of about 4.1×1011cm−2. The samples are essentially free of trapping in the AlAs, as indicated by the almost complete lack of hysteresis in theCVcurves. At room temperature under steady‐state illumination we see both a voltage shift and a peak in theCVcurves. The shift is attributed to the formation of an inversion layer, while the peak is believed due to the ac response of space charge flowing through the AlAs. In contrast to recent reports on similar samples grown by metalorganic chemical vapor deposition, the MBE grown samples appear to be suitable for fabricating field‐effect devices.