Electrical transport measurements are very sensitive to the structure of a heterojunction. This sensitivity is used in conjunction with a realistic model for the band diagram to determine the position of the dopant junction relative to the metallurgical junction. This electrical technique involves the determination of an effective barrier height from temperature-dependent I-V measurements and comparison with calculated barrier heights. The sensitivity of the electrical characteristics to the device structure can often be greater than that of secondary ion mass spectroscopy or C-V profiling. GaAs/Al 0.30Ga0.70 As p+-n heterojunctions grown under a variety of conditions are used to demonstrate this technique. Growth conditions which produce abrupt zinc profiles are discussed.