Preparation And Photoelectric Properties Of AlN Thin Films On Si(110) Substrate By Laser Molecular Beam Epitaxy

AlN thin films have broad application prospects in optoelectronics and microelectronics due to its excellent properties.Single crystal Si has been widely used in the field of microelectronics,compared with Si(111)and Si(100),there are smaller lattice mismatches and thermal mismatches betwe en Si(110)and AIN.Therefore,epitaxial growth of AIN films on Si(110)substrate can reduce the defect density of the film and improve its crystal quality.AIN films were deposited on Si(110)substrate by laser molecular beam epitaxy technique.The effects of different process parameters on the crystal quality,surface morphology,optical properties and electrical properties of AIN films were investigated,the results are as follows:1.Cubic zinc-blende AIN films with the single preferred of(200)plane were deposited on Si(110)substrate by laser molecular beam epitaxy technique.The orientation relationship of cubic AlN films and Si(110)substrate is AlN(100)//Si(110).For the lattice mismatch between Si(110)substrate and cubic AlN films,there exists misfit stress in the cubic AIN films.The preferred process parameters for preparing a high quality cubic AIN film are:substrate temperature of 750?,nitrogen partial pressure of 0.5 Pa,and laser frequency of 8 Hz.The interface between cubic AlN films and Si(110)substrate is clear and smooth,the AIN films has a strained layer having a thickness of approximately 67 nm adjacent to the Si(110)substrate.2.The reflectivity of the cubic AIN films in the visible region is about 45%,the cubic AIN films deposited under the same process parameters has a very obvious absorption peak at a wavelength of about 260 nm.Based on the reflection spectrum of cubic AIN films,the bandgaps of cubic AIN films deposited under different process parameters was obtained,which decrease as the increasing of lattice distortion.3.The photoluminescence spectra of cubic AIN films have two luminescence peaks in the blue region at 420 nm and the green region at 500 nm,respectively,and the corresponding energies are-2.95 eV and-2.48 eV,respectively.The luminescence peak of the film in the 420 nm blue region is generated by the deep transition of VN from the shallow level to the ON-VAl(Al vacancy).The luminescence peak around 500 nm in the green region is composed of radiation between VAl and the valence band.4.The cubic AIN film prepared by laser molecular beam epitaxy is a p-type semiconductor.The AlN/Si(110)p-n junction has good rectification characteristics.The log-log fitting of the I-V curve shows that the current transfer mechanism of the p-n junction conforms to the space charge-constrained conduction mechanism.5.The EL spectra of AlN/Si(110)p-n junction shows that the film has yellow-green light emission in the range of 500 nm-600 nm,the strongest center of luminescence is 531 nm,and the corresponding composite energy is E=2.34 eV.As the current increases,the luminous intensity also increases.When the forward current is 32 mA,the heterojunction has the strongest luminescence intensity.