Preparation And Research On Photoelectric Properties Of NiO/SiC Heterojunction

NiO is a natural p type direct band gap semiconductor material.It has many advantages,such as large band gap(3.6eV?4.0eV),good chemical stability and so on.It has been widely studied and applied in the fields of light emitting diode,detector,laser,solar cell and gas sensor.In view of the low injection efficiency of the p+-n emitter in SiC bipolar device at room temperature,the use of NiO instead of p SiC as the p+ emitter can effectively improve the injection efficiency of the emitter.In this paper,NiO thin films were deposited on 4H-SiC substrate by magnetron sputtering,and p-NiO/n-SiC heterojunction was fabricated.The photoelectric properties of NiO/SiC heterojunction were studied.The main work and results are as follows:1.NiO thin films were prepared on n 4H-SiC(0001)substrates by magnetron sputtering.The results show that the prepared NiO film is a polycrystalline structure.When the ratio of argon to oxygen is 1:1,NiO appears(200)crystal orientation,the film is smooth and compact,the grain size is uniform about 15nm,the conductive type of NiO thin film is p,the width of the optical band gap is about 3.75eV,and the resistivity is 0.051?·cm.2.The p-NiO/n-SiC heterojunction was successfully prepared and the p-NiO/n-SiC heterojunction band diagram was constructed.The conduction band difference(AEc)and valence band difference(?Ev)of the SiC and NiO were calculated to be 1.64eV and 1.15eV respectively.The results showed that the cavity injection capacity of the prepared p-NiO/n-SiC heterojunction was 1.53 × 108 times higher than that of the SiC pn junction.3.The electrical properties of p-NiO/n-SiC heterojunction were studied.The results show that the prepared heterojunction has good rectifying characteristics and the opening voltage is about 1.4V.The results of variable temperature I-V show that the opening voltage and ideal factor of p-NiO/n-SiC heterojunction decrease with the increase of temperature,and the transmission mechanism of the current is changed from the ohm transmission mechanism in the low bias zone to the composite tunnel conducting mechanism in the high bias zone.4.The photoelectric properties of NiO/4H-SiC heterojunction were studied,and the photoelectric properties of heterojunction were improved by introducing NiO i layer at the interface.The results show that the introduction of NiO i layer effectively improves the photoelectric properties of heterojunction,and the ratio of light to dark current is increased by 3 times.