Fabrication And Ohmic Contact Of Wide Band-gap Semiconductor Materials

Boron nitride and aluminum nitride are wideband gap semiconductor materials with good physical and chemical properties,which have broad application prospects in the fields of deep ultraviolet optoelectronic devices and high-frequency high-power rf devices.With the deepening of research,although the device research based on aluminum nitride material has made great progress,the ohmic contact research of the device is slow due to the nearly insulating semiconductor material characteristics of aluminum nitride itself.Hexagonal boron nitride is even more difficult to prepare,but its band gap of 6.5ev determines that this material has a good application prospect in the fields of deep ultraviolet LED,ultraviolet LD,surface acoustic devices and high-temperature microblogs and high-power devices.Deep ultraviolet LED is a rapidly rising semiconductor optoelectronic device in recent years,which has the characteristics of small space,high brightness,high luminous efficiency and environmental protection,and is an ideal substitute for mercury lamp.We hope to achieve excellent ohmic contact on the basis of the third generation semiconductor,which is one of the key technologies to achieve the performance improvement of the above devices,and is also a problem that the industry has been eager to solve.In this work,firstly,we treated the semiconductor surface with oxygen plasma on the unintentionally doped aluminum nitride/sapphire template material grown by high temperature HVPE.Then,the metal-semiconductor contact structure was formed by evaporating Pd/Al/Au metal electrode structure and rapid annealing at 700-1000 C for 30 seconds in nitrogen.The structure was characterized by SEM and XRD to study the effect of alloy mode and alloy proportion on ohmic contact.The experimental results show that the specific contact resistivity is the lowest when annealing temperature is 900?,reaching 3.01?·cm2.The morphology of PdAl alloy and its more uniform and smooth surface can be observed at this time.In order to determine the role of oxygen plasma modification in ohmic contact,a comparative experiment was carried out,that is,no oxygen plasma treatment was performed on the semiconductor surface before evaporation,and ICP etching was performed on the samples to avoid the influence of oxygen elements in the environment.The results show that the ohmic contact is obtained at 950?,and the specific contact resistivity is 11.01?·cm2.This result is also confirmed by first-principles calculation.First,BN epitaxy layer was grown on the substrate and characterized,including scanning electron microscopy(SEM),transmission electron microscopy(TEM),fluorescence spectroscopy(EDS),Raman spectroscopy(Raman)and cathodoluminescence(CL).Experiments show that although the samples grown by our growth method contain impurities such as oxygen and carbon,they still make the epitaxy layer grow closer to the single crystal form.The wavelength of impurity peak is also in the ultraviolet region,which proves that the materials can be used as materials for ultraviolet light emitting devices.