Photothermoelectric Effect Observed In Mos Structure

Metal-oxide-semiconductor(MOS)structure,is formed by growing or depositing a layer of insulating film on the surface of semiconductor substrate,which is covered with a certain area of conductive layer.MOS devices have attracted much attention due to their unique photoelectric properties.In 1959,the MOS structure was proposed as a semiconductor variable capacitor.Later,with the continuous development of MOS structure research,it became an important structure in the study of the semiconductor and insulating film interface,the semiconductor surface layer and the electronic motion in insulating film.Microelectronic components are widely used in military,daily life and other fields due to its high performance,high reliability,small volume and low cost.Among many MOS structures,silicon substrate is also widely studied.In this paper,a6.0 nm thick Ti film was prepared on a naturally oxidized silicon substrate by DC sputtering.The photothermoelectric effect(PTE)of Ti/SiO₂/Si structure in MOS structure was studied,mainly including the following two parts:1.The thermal resistance effect of laser-induced Ti/SiO₂/Si structure.The photothermoelectric resistance effect of Ti/SiO₂/Si structure was studied.In the experiment,a 10.6?m carbon dioxide laser was used to irradiate on the surface of the sample,and the photothermoelectric resistance effect was found.And the transient response of the resistance was measured and observed.When using a digital ohmmeter to measure the thermal resistance of Ti/SiO₂/Si structure,the battery inside the ohmmeter will applied positive or negative bias to the sample.Then,the data of thermal resistance changing with time under positive and negative bias were studied respectively.The variation of thermal resistance changing with time under positive/negative bias was discussed,and the theoretical analysis was carried out with the theory of electron motion.The data of positive and negative bias was compared and analyzed.The results show that the Ti/SiO₂/Si structure has obvious photothermoelectric effect,which is expected to have potential application prospects in the field of thermal effect devices.2.The thermal voltage effect of Ti/SiO₂/Si structure.The photothermoelectric voltage effect of Ti/SiO₂/Si structure was studied.In the experiment,a visible laser with wavelength of 650 nm was used to irradiate on the surface of the sample to observe the thermal voltage effect.There are two indium electrodes on the surface of the sample,and the photovoltage between them has a linear relationship with the laser irradiation position.At different laser irradiation points,the data of photoelectric voltage changing with time was recorded by digital ohmmeter.The dynamic process of thermal voltage effect from generation to stabilization was analyzed,which is similar to the phenomenon induced by the carbon dioxide laser.However,the rise time of photothermoelectric voltage induced by visible laser is seconds level,and that of CO₂ laser is tens of seconds level.From the perspective of electron movement,the relationship between the saturation time of the photovoltage and the laser irradiation point was explained.In order to further research the photothermoelectric voltage effect,the visible lasers of different power were used to irradiate on the same position,and the time response of photovoltage was observed.These results show that Ti/SiO₂/Si structure has a broad application prospect in the field of optoelectronic devices.