Influence comparison of N2 and NH3 nitrogen sources on AlN films grown by halide vapor phase epitaxy

A comparison of the nitrogen sources(N2 and NH3)influence on AlN films grown by high-temperature halide vapor phase epitaxy(HVPE)is reported.The x-ray rocking curves(XRCs)indicate that the full width at half maximum(FWHM)of(0002)plane for AlN films using N2 as nitrogen source is generally smaller than that using NH3.Optical microscope and atomic force microscope(AFM)results show that it is presently still more difficult to control the crack and surface morphology of AlN films with thicknesses of 5-10µm using N2 as the nitrogen source compared to that using NH3.Compared with one-step growth,two-step growth strategy has been proved more effective in stress control and reducing the density of threading dislocations for AlN epilayers using N2 as the nitrogen source.These investigations reveal that using N2 as nitrogen source in HVPE growth of AlN is immature at present,but exhibits great potential.

Halide vapor phase epitaxy of monolayer molybdenum diselenide single crystals

Single-crystalline transition metal dichalcogenides(TMD)films are of potential application in future electronics and optoelectronics.In this work,a halide vapor phase epitaxy(HVPE)strategy was proposed and demonstrated for the epitaxy of molybdenum diselenide(MoSe_(2))single crystals,in which metal halide vapors were in-situ produced by the chlorination of molybdenum as sources for the TMD growth.Combined with the epitaxial sapphire substrate,unidirectional domain alignment was successfully achieved and monolayer single-crystal MoSe_(2) films have been demonstrated on a 2-inch wafer for the first time.A series of characterizations ranging from centimeter to nanometer scales have been implemented to demonstrate the high quality and uniformity of the MoSe_(2).This work provides a universal strategy for the growth of TMD single-crystal films.