Data for "Constant photocurrent method to probe the sub-bandgap absorption in wide bandgap semiconductor films: the case of α-Ga2O3"

Here we present a revival of the constant photocurrent method to measure sub-bandgap absorption in wide bandgap semiconductor films. The method involves maintaining a constant photocurrent by continually adjusting the impinging photon flux across the energy spectrum. Under such conditions, the reciprocal of the photon flux for uniformly absorbed light is proportional to the absorption coefficient. This method is applied to α-Ga2O3 and reveals that it can access the absorption coefficient from 1x105 cm-1 at the band edge (5.3 eV) to 0.8 cm-1 close to mid-bandgap (2.7 eV). Changes in the steepness of the absorption curve in the sub-bandgap region are in excellent agreement with defect states of α-Ga2O3 reported by deep level transient spectroscopy, indicating the technique shows promise as a probe of energetically distributed defect states in thin film wide bandgap semiconductors.