The Study On Photoelectric Behavior Of GaN Film By Surface Photovoltaic Spectroscopy

As one of the most promising short wavelength photoelectronic materials,GaN is a direct bandgap semiconductor whose forbidden band width is 3.39eV at room temperature.Because of its high temperature resistant,corrosion resistance,high electron saturation drift velocity and good thermal conductivity,GaN is suitable for manufacturing semiconductor LED,LD and other opto-electronic devices,high-temperature,high-frequency,high power electronic devices. Recent research reports that GaN-based materials have great potentials in high conversion efficiency multi-junction solar cell whose theoretical efficiency is 86.8%.This will be another research hotspot.It's necessary to study the electronic construction and photoelectric behavior of surface and interface of GaN film for the theory and application research.The properties of the photovoltaic materials,such as bandgap,conductive type,surface states,minority carrier diffusion length,can be obtained by analyzing the change of semiconductor surface photovoltage.SPV technique is non-destructive,quick and highly sensitive.Measurements using SPS can be performed at any reasonable temperature,on any semiconductor material,at any ambient.In a word,SPS is an irreplacable measurement method for analyzing the photoelectric behavior of semiconductor materials.In the present work,we established a set of surface photovoltage test system based on Kelvin probe and studied the properties of photo-induced charge carriers in GaN film.SPV technique has been applied to investigate the separation and the transport mechanism of the photo-induced charge carriers in GaN films which were grown on theα-Al₂O₃ substrate and the ITO substrate by ECR-PEMOCVD.The different results between these films observed on Kelvin probe and MIS construction were discussed.A study of the surface work function and time resolved photovoltage of the GaN films were carried out on Kelvin probe.From this study we conclude that indicate that the crystal construction and physics properties of GaN films are significantly different with the different substrates,at the same time,the transport and recombination of the photo-induced carriers in the surface and interface of the GaN films are deeply affected.Therefore,these results provide the scientific experiment fact for the further study and application of GaN materials.Moreover,these results can provide some theoretical evidences for the design of the high performance optoelectronic devices.