Surface Photovoltage Spectroscopy. Method and Applications.

The investigation of surface space-charge properties (charge depletion, accumulation or inversion etc..), defect states (which have a detrimental effect on doping) and electronic properties of InN-based quantum wells and heterostructures (electronic transport at interfaces, quantum confinement) are among the main objectives of the RAINBOW Project. Surface photovoltage spectroscopy (SPS) is a powerful method for obtaining a detailed picture of the electronic structure of surfaces, defects and interfaces [1]. In SPS, changes in band bending (both at the free semiconductor surface and at buried interfaces) are monitored as a function of external illumination. Surface photovoltage spectroscopy can provide detailed, quantitative information on bulk properties (e.g. bandgap and type, minority carrier diffusion length and lifetime) and can be used for a complete construction of surface and interface band diagrams, including the measurement of energy levels in quantum structures. A particular strength is that a comprehensive analysis of surface and bulk defect state distributions and properties is made possible. Measurements using SPS are contactless and non-destructive. In the present contribution the relevant surface and interface theory, the physical principles of the method and the experimental details will be discussed, together with several applications concerning a wide variety of materials, alloys and low dimensional semiconductor structures. [1] L Kronik and Y Shapira, Surface photovoltage spectroscopy of semiconductor structures: at the crossroads of physics, chemistry and electrical engineering, Surf. Interface Anal. 2001; 31: 954–965.