The Measurement And Modulation Of Lateral Photovoltaic Effect In A-Si:H/c-Si P-i-n Structure

The lateral photovoltaic effect(LPE)refers to the voltage detected from the same side of a junction,p-n junction,metal semiconductor junction or semiconductor heterojunction,when laser beam focuses on a spot at the surface of the junction.Due to the output of the lateral photovoltaic(LPV)changes linearly with the laser spot position,this effect can be used in position-sensitive detectors(PSD).The research about a-Si:H/c-Si p-i-n structure is originated form solar cells and now this structure has been used in many kinds of optoelectronic devices since its low cost and high conversion efficiency.In this paper,we report a new application of a-Si:H/c-Si p-i-n structure in LPE.The main work is as follows:1.It is found that laser power,wavelength and contact distances have a great influence on position sensitivity.The position sensitivity increases linearly in low laser power region and then the growth rate slows down with increasing laser power until saturate.Besides,the longer wavelength we use,the higher of position sensitivity we can get when illuminated with the same laser power.What's more,position sensitivity is irrelevant with contact distance in low power region but decreases with it in high power region.2.The LPE can be enhanced greatly with the aid of an external bias voltage.The electric field caused by this bias voltage can be seen as a uniform field since the good conductance of ITO film and Ag film.The result shows that position sensitivity goes up dramatically with increasing bias voltage at the same power.If the bias voltage is high enough,position sensitivity is not dependent on contact distance anymore but changes linearly with laser power.3.We also found that temperature has a significant impact on LPE when detecting in a cryostat cooled by liquid nitrogen.The experiment demonstrates that position sensitivity decreases with temperature at the same laser power.The explanation for this phenomenon is that the decreasing build-in electric field in lower temperature leads to fewer holes transited into ITO.Therefore,a-Si: H/c-Si p-I-n structure shows a large LPE and a good linearity in our experiment.Bias modulation is an effective method in enhancing LPE,which may promote the development of multifunctional PSD.Although we can not obtain high sensitivity at low temperature yet,it is an effective theory for the study of PSD working in the extreme environment in the future.