A representative number of abrupt GaAs junctions, asymmetrically doped, have been studied to delineate quantitatively the properties of spectra (called shifting‐peak spectra) whose peak energy approximately equals the applied voltage V, and shifts in position and intensity with V. The free‐electron concentration n on the more lightly doped side was varied from 3×1017 cm−3 to 8×1018 cm−3, the voltage range was ∼1.0 to ∼1.5 V, and the temperature was varied from 12° to 255°K. Because the active region width is 600 Å or less, and the spectral shape agrees in all details with Morgan's theory of photon‐assisted tunneling, these shifting‐peak spectra have been identified as radiative tunneling. It is shown here that no adjustable parameters are needed to calculate the experimental spectral shape when only T, V, and n are specified. This means that for any given temperature, n alone represents the influence of the junction on the spectral shape, while the independent parameter in terms of excitation is the voltage and not the current, as usually stated. The agreement between the calculated and experimental spectra includes the logarithmic slope of the low energy tail, and the difference between V and the energy of the peak‐emission intensity hvp: eV0=eV‐hvp. This agreement emphasizes the necessity of including the parabolic junction potential as obtained from Poisson's equation when calculating the tunneling‐hole and electron‐wave functions. The usual simplifying assumption of a linear potential is inadequate. To clarify previous observations of one or two types of shifting‐peak spectra, linear‐graded and abrupt‐asymmetrical junctions were made from adjacent wafers of the same crystal, and the resulting shifting‐peak spectra were compared. Only band‐to‐band radiative tunneling was observed for the abrupt junction, but for the linear‐graded junction two shifting‐peak spectra were observed. In the low excitation region for linear‐graded junctions, the shifting‐peak spectra may be described by band‐to‐impurity radiative tunneling that results in a narrow active‐region width, while at higher bias the emission becomes band‐to‐band radiative tunneling with a wider active region. These results demonstrate that shifting‐peak spectra previously attributed to band filling may be described in terms of photon‐assisted tunneling.