New Experimental Approach to The Excess Carrier Transfer in Semiconductor Structures Based on Time Resolved Photovoltage

Abstract

The photovltage developed along the plane of the translational invariance (longitudinal one) of the semiconductor layers due to the illumination was widely investigated in variety of GaAs/AlGaAs multi-quantum well structures. In the structures with perfect quality there should be no photovoltage, so an criterium of material quality can be derived from such kind of longitudinal photovoltage measurements. Vice-versa, in the low quality materials there exists large photovoltage signal which is related to the barrier height of random doping fluctuations [1]. The previous experimental investigations concerned only the dependence of the photovoltage of temperature and illumination intensity. The sign change of the photovoltage is observed only as a function of the temperature. Despite of the suitably developed theory of many junction material (JUNC) [2], still there exist difficulties in the explanation of the sign changes. We believe that the experiment could be improved using approptiate monochromatic light instead of white one. In this work we describe a new experimental approach in this trend which is based on transient measurements of both photoconductivity and SC photovoltage at different wavelengths. Since the wavelength scanning in the subbband gap excites consecutively the existing deep levels that will contribute for the clarification of deep level behaviour.