Energy gap and carrier concentration are among the most important material parameters governing the electrical performance of AlGaAs/GaAs heterojunction devices. A novel technique for profiling aluminum mole fraction ratio and carrier concentration is presented which is based on point contact current voltage (PCIV) measurements. The method measures point contact voltages at a preselected current as a function of depth. A composition profile is then created by referring to appropriate calibration samples. The PCIV technique is rapid, inexpensive, and offers high spatial and depth resolution. Additionally, both the aluminum mole fraction ratio and the carrier concentration can be obtained sequentially from the same measurement. The application of this technique to several device structures of current interest is presented.